Transcript for:
Aldehydes and Ketones

aldehydes and ketones are organic compounds that contain carbon oxygen double bonds that is the carbonyl group as a functional group they have the general molecular formula cnh2n Oh aldehydes and ketones closely resemble each other in most of their chemical properties hence they are often collectively referred to as carbonyl compounds aldehydes and ketones differ in the nature of the groups that are attached to the carbonyl group in aldehydes one of the two available valances of the carbonyl group carbon is essentially satisfied by an each atom and the other by a hydrogen atom an alkyl group or an adroit crew hence the general formula for aldehydes is our C double bond o H if our is H then the corresponding aldehyde is formaldehyde if our is the methyl group then it is an acetaldehyde and if R is the phenyl group then it is a benzaldehyde in Ketones the two balances of the carbonyl group are satisfied by two alkyl or aryl groups r & r - which may be the same or different if our and our - both represent the same group then the ketone is called a simple ketone if R and R - are different then the ketone is called a mixed ketone the general formula for ketones is our C double bond o R - for example acetone represents a simple ketone where both R and R dash are the same that is ch3 benzophenone we're both r and r - r c6h5 also represents a simple key tool on the other hand acetophenone where r is a methyl group and - is a phenyl group represents a mixed Cato due to this difference in the nature of the groups attached to the carbonyl group in aldehydes and ketones their reactivity is different for example aldehydes oxidize with ease as compared to ketones you let us now look at the significance of these compacts aldehydes and ketones are well known for their fragrance and flavor for example the smell of acetaldehyde is reminiscent of apples also vanillin slum vanilla beans salicyaldehyde from Meadows sui and cinnamaldehyde from cinnamon have very pleasant fragrances you aldehydes and ketones both find significance in several biochemical processes for example glucose a polyhydroxy aldehyde is the chief product in photosynthesis respiration which takes place via the combustion of glucose is associated with the liberation of energy does it is the ultimate source of energy in plants and animals these compounds have considerable industrial significance they are used as solvents and a starting material for the synthesis of several other products for example acetone 1/8 I met a ketone our common industrial solvents formaldehyde is used to prepare bakelite urea formaldehyde glues and other polymeric products acetaldehyde is chiefly used as starting material for the synthesis of acetic acid hi acetate drugs and polymers benzaldehyde is used in the perfume and dye industries certain compounds are used for preparing adhesives beans resons Plastics fabrics and so on like other organic compounds anti hides and ketones also have two systems of nomenclature we are comment system and the IUPAC system the common names of Andy Heights are derived from the names of the corresponding carboxylic acids that they form on oxidation they are named by replacing the icy acid of carboxylic acid by aldy height does the aldehydes formaldehyde acetaldehyde and benzaldehyde uh named after formic acid acetic acid and benzoic acid respectively as you can see they are named by replacing the suffix IC acid with an D height the positions of the side chains all substituent's in the carbon chain of anti hides are indicated by the Greek letters alpha beta gamma and Delta the carbon that is directly linked to the aldehyde group is alpha carbon the next carbon is beta carbon and so one for example the given compounds can be named alpha hydroxy butyl anti height and beta brahma-bhutah aldehyde respectively in the IUPAC system aldehydes are named by replacing the e of the corresponding alkane by a L hence the IUPAC name for aldehydes is al canal for example the IUPAC name for formaldehyde can be written by replacing the letter e of the corresponding alkane methane by al hence the IUPAC name for formaldehyde is methanol similarly the IUPAC names for acetaldehyde propene LT height n-butyl aldehyde isobutyl aldehyde and valor aldehyde our ethanol propanol butanol 2-methyl propanol and Penton and respectively the substance in the aldehydes are prefixed in alphabetical order along with numerals indicating the positions in the carbon chains does the IUPAC name of the given compound can be written as three bromo - plural for Mathai hexanol in case of Andy hides the longest carbon chain is number starting from the carbon of the aldehyde group does the given compound is named to Ethel three-meat hi Pantanal it must be noted that the c2 of the IUPAC name corresponds to the Alpha of the common name for example the compound shown here bears the IUPAC name of two methyl Pantanal while it's common name is alpha metal valor NT height you here is a list of some aldehydes with their common and IUPAC names from the list you can see that the IUPAC names run for chloro acetaldehyde is 2-chloro ethanol and for acrolein it is probe to inhale in the IUPAC system when the aldehyde group is attached to the ring the suffix carbonyl T height is added after the name of the cycloalkane for example in cyclohexanol d height the aldehyde group is attached to a six member cyclohexane drink hence its RUP AC name can be written by adding the suffix carb aldehyde to the cyclohexane that is cyclohexane carbon and e height similarly the IUPAC name for benzaldehyde can be written as benzene carbon d height note that the common name benzaldehyde is also accepted by our UPA see to indicate the substituent on the ring the numbering of the ring starts from the carbon atom to which the aldehyde group is attached for example the IUPAC names for gamma methylcyclohexane aldehyde is 3 methylcyclohexane carbon d height similarly while writing the IUPAC name for ortho hydroxy then sandy height or Sally salary height the substituent hydroxyl group gets the second position as the numbering of the ring starts from the carbon atom attached to the Andy height group does the IUPAC name for this molecule is to hydroxybenzene carbon the height now let's look at the common names and the IUPAC names of some compounds the common name meta chlorobenzene height is written as three chlorobenzene carb aldehyde in the IUPAC system similarly bad a night Rubens aldehyde is for nitrobenzene carb aldehyde Talon D Hyde is benzene one to die carb aldehyde vanillin is for hydroxy 3 method see benzine carb aldehyde Croton aldehyde is 2 butanol and cinnamaldehyde is three fin i probe to inhale let us now turn our focus to the nomenclature of ketones in the comment system ketones are named simply by adding the suffix ketone to the name of the two alkyl groups in case of simple ketones we're both the alkyl groups are the same the prefix die is used for the alkyl group for example the compound ch3 C double bond o ch3 is named dimethyl ketone or simply acetone while c2h5 C double bond o c2h5 is named diethyl ketone in case of mixed ketones the two different alkyl groups R and R - a mentioned in alphabetical order for example the compound ch3 C double bond o c2h5 is named ethyl methyl ketone similarly ch3 C double bond o c3h7 is named methyl n pro pi ketone the positions of substitutes in ketones are indicated by the Greek letters alpha alpha - and Beta Beta - and so on we're alpha-alpha - are given to the carbon atoms and to sent to the keto group for example in the given molecule the substituent's two bromine atoms are present on the alpha dash and beta carbons hence it is named alpha - beta die bromo diethyl ketone alkylphenol ketones are usually named by adding the acyl group as a prefix to fin on for example when ch3 C double bond o is attached to benzene drink it is named acetophenone similarly the molecule c2h5 C double bond o c6h5 is named through POV known the ketone in which a carbonyl group is attached to two benzene rings is named benzophenone according to the IUPAC system ketones are named by replacing the e of the corresponding alkene with own the longest chain carrying the carbonyl group is considered the parent chain and the numbering begins from the end nearer to the carbonyl group the compound shown here is named for me tile xn3 one in certain poly functional compounds if the carbonyl functional group of the ketone is present as a substituent then it can be indicated by the prefix ox o and a number is indicated to show its position in a molecule the example here contains three functional boobs I dropped some aldehyde and keitel according to IUPAC rules as the order of preference while naming is anti height ketone and then hydroxy the carbonyl functional group of the ketone and the hydroxyl group of the alcohol are treated as substitutes hence the IUPAC name is five hydroxy for Doxil hexanol as aldehydes and ketones contain the same carbonyl group their properties and methods of preparation are quite similar methods for the preparation of auntie hides and ketones include oxidation of alcohols dehydrogenation of alcohols of alkenes hydration of alkynes reduction of acid chlorides and reduction of nitrites let us learn about each one of these in detail let us begin our discussion with the preparation of carbonyl compounds from alcohols you have already learned that primary and secondary alcohols yield aldehydes and ketones on oxidation the process of oxidation of alcohols involves the loss of alpha hydrogen that is the hydrogen atom attached to the carbon bearing the Oh each group in the presence of reagents such as palladium chlorochromate BCC or a certified potassium dichromate or acidified potassium permanganate now since primary alcohols contain two alpha hydrogen's they can either lose one of them to form an aldehyde selectively in the presence of palladium pure or crewmate PCC or can lose both of them to form a carboxylic acid in the presence of acidified potassium permanganate the conversion of a primary alcohol into an aldehyde is difficult because aldehydes are susceptible to further oxidation one of the best reagents for the conversion of primary alcohols into aldehyde is PCC note that the oxidation of primary alcohol to carboxylic acids is usually accomplished by the use of acidified potassium permanganate for example ethanol on oxidation with PCC gifts ethanol but gives ethanoic acid in the presence of acidified potassium permanganate on the other hand a secondary alcohol loses its only one alpha hydrogen to form a ketone in the presence of acidified potassium dichromate for example isopropyl alcohol on oxidation in the presence of acidified potassium dichromate gifts troponin or acetone another method of preparing carbonyl compounds from alcohols is by the dehydrogenation of alcohols this method is suitable for the oxidation of volatile alcohols it involves passing vapors of an alcohol over metal catalysts like silver or copper dehydrogenation of primary alcohols yields aldehydes while that of secondary alcohols yields ketones for example when vapors of ethyl alcohol are passed over heated copper at 573 Kelvin dehydrogenation takes place and ethanol is formed however isopropyl alcohol yields as a tune on dehydrogenation carbonyl compounds can also be prepared from the ozonolysis of alkenes Bo's analysis involves the cleavage of the double-bond by the addition of ozone to give a slightly product called also night followed by hydrolysis in the presence of zinc danced depending upon the substitution pattern of alkenes Moses eels either aldehydes or ketones or both for example 2-butene eels two molecules of acetaldehyde on ozonolysis y23 dimethyl Butte - in eels two molecules of acetone a molecule such as 2-methyl 2-butene yields a mixture of acetaldehyde and acetone on ozonolysis hydration of alkynes is yet another method for the preparation of carbonyl compounds this method involves the addition of water to alkynes in the presence of mercuric sulfate and sulfuric acid to form aldehydes or ketones as the final product for example acetylene on hydration gives unstable vinay alcohol which tautomer rises to form the acetaldehyde all other alkynes yield ketones in similar manner for example propane gives acetone on hydration carbonyl compounds can also be prepared by the reduction of acid chlorides aldehydes can be prepared by the reduction of acid chlorides with hydrogen in the presence of palladium on barium sulfate in Quinlan this reaction is called rosin Mons reduction aliphatic and aromatic aldehydes can be prepared by this method note that ketones cannot be prepared by this method for example adding hydrogen to acetyl chloride in the presence of palladium on barium sulfate in Quinlan Eels acetaldehyde similarly rosin Mons reduction of benzoyl chloride gives benzaldehyde ketones on the other hand are prepared by the treatment of acid chlorides with dialkyl cadmium dialkyl cadmium can be prepared by the reaction of cadmium chloride with grignard reagents for example the reaction of methyl magnesium bromide with cadmium chloride gives dimethyl cadmium the treatment of dangit i cadmium with proven oil chloride gives a tiny ethyl ketone aldehydes and ketones can both be prepared from nitriles let's see how aldehydes can be prepared by the reduction of nitriles to i mines followed by hydrolysis the reduction of a nitrile to the corresponding imine by stannous chloride in the presence of hydrochloric acid followed by hydrolysis to ield the corresponding aldehyde is known as the stiffened reaction for example attained nitrile on production in the presence of sncl2 and HCL gives at any mean this on hydrolysis in the presence of an acid gives ethanol as the final product alternatively selective reduction by dye isobutene aluminium hydride di b al h 2 i mines followed by hydrolysis also eat aldehydes for example attained nitrile reduction in the presence of di ba l h followed by hydrolysis yields ethanol similarly DIBL each can also be used to reduce esters to aldehydes as shown here ketones on the other hand can be prepared by treating an I try with the grignard reagent followed by hydrolysis for example propafenone can be prepared by treating propane nitrile with phenol magnesium bromide in ether followed by hydrolysis there is now look at the preparation of aromatic aldehydes and ketones aromatic aldehydes can be prepared from benzene or aromatic acid chlorides or methyl benzene or from benzyl halides let us discuss each method aromatic aldehydes can be prepared by treating benzene all its derivatives with carbon monoxide and dry hydrogen chloride gas in the presence of anhydrous aluminium chloride or cuprous chloride this reaction is known as the gatim and coach reaction for example benzaldehyde can be prepared by treating benzene with a mixture of carbon monoxide and dry HCl gas in the presence of anhydrous alcl3 as you have seen earlier Rosenman reduction of benzoyl chloride with hydrogen in the presence of palladium on barium sulfate in quinidine also gives benzaldehyde benzaldehyde more substituted benzaldehyde can also be prepared by the oxidation of methyl benzene with chromite chloride to a chromium complex followed by hydrolysis this reaction is known as the e tarde reaction benzaldehyde can also be made from toluene wentao lien or substitute italian is treated with chromic oxide in acetic anhydride benzidine diacetate is formed this on hydrolysis in the presence of an acid eels the corresponding benzaldehyde the hydrolysis of benzyl halides also eels aromatic aldehydes for example the hydrolysis of benzyl chloride which is obtained by the sidechain halogenation of Colleen gifts benzaldehyde remember that this is the commercial method for manufacturing benzaldehyde aromatic ketones are more conveniently prepared by the friedel-crafts isolation benzene reacts with acid chloride in the presence of anhydrous aluminum chloride to give the corresponding ketone this reaction is known as the friedel-crafts isolation for example benzene reacts with acetic oh right and benzoyl chloride in the presence of anhydrous aluminium chloride to give acetophenone and benzophenone respectively the physical and chemical properties of aldehydes and ketones are determined by the structure of the carbonyl group it is therefore very important to understand its structure like the carbon-carbon double bond in alkenes carbon-oxygen double bond of the carbonyl group is composed of one Sigma bond and one PI bond the carbon atom in the carbonyl group undergoes sp2 hybridization in its excited state leaving one out of three P orbitals are hydrolyzed the carbon to oxygen Sigma bond is produced by the overlap of one sp2 orbital off carbon with a p-orbital of oxygen on the other hand the carbon to oxygen pi bond is formed by the sideways overlap of the P orbitals of carbon and oxygen remaining to sp2 orbitals of carbon form to Sigma bonds with the S orbital of hydrogen as in formaldehyde one Sigma bond with the S orbital of hydrogen and another Sigma bond with an sp3 orbital of the carbon of the alkyl group like in other aldehyde or to Sigma bonds with two sp3 orbitals of the carbon of the alkyl group as in ketones does the carbonyl carbon and the three atoms attached to it lie in the same plane with a trigonal coplanar structure and a bond angle of 120 degrees why the PI electron cloud lies perpendicular above and below the plane it is important to note that the carbon-oxygen double bond in the carbonyl group is different from the carbon-carbon double bond in alkenes in case of alkenes the by electron cloud is equally shared by two atoms whereas in the carbonyl group the PI electron cloud is attracted more towards the oxygen atom due to its greater electronegativity consequently in the carbonyl group the oxygen atom acquires a partial negative charge while the carbon atom acquires a partial positive charge thus making the carbonyl a polar group with the dipole moment value of 2.3 to 2.8 d by units however the high value of the dipole moment can be accounted for both the inductive effect and the resonance effect now let us look at the physical properties of carbonyl compounds at room temperature formaldehyde is a gas and acetaldehyde is a volatile liquid the aldehydes and ketones are liquids or solids and room temperature aldehydes and ketones have higher boiling points than hydrocarbons and eaters of comparable molecular weights this is due to the weak intermolecular dipole-dipole interactions observe this table about compounds of almost similar molecular weights 72 to 74 we see that nonpolar hydrocarbons like n-pentane and weakly polar diethyl ether have lower boiling points than that of polar and butyraldehyde and ethyl methyl ketone however their boiling points are lower than that of n beauty alcohol and propionic acid this is because carbonyl compounds are not capable of forming intermolecular hydrogen bonding by themselves since they contain hydrogen bonded to carbon but not to oxygen aldehydes and ketones are soluble in the usual organic solvent like benzene ether and chloroform [Music] to know their solubility in water lesser to this table which shows the solubility of a compound in grams per 100 grams of water we see that the lure and II Heights and ketones such as formaldehyde at aldehyde and acetone because of their ability to form hydrogen bonding with water are miscible in water in all proportions notice that solubility decreases with an increase in the length of the carbon chain the lower aldehydes and ketones have a characteristic pungent odor with an increase in the size of the molecule the order becomes less pungent and more fragrant therefore many naturally occurring aldehydes such as vanilla from vanilla beans and cinnamaldehyde from cinnamon and ketones such as acetophenone are used to blend perfumes and as a flavoring agent as both aldehydes and ketones contain the carbonyl group they resemble each other closely in most of their properties the carbonyl group governs the chemistry of aldehydes and ketones in two ways [Music] by providing a site for nucleophilic addition and [Music] by increasing the acidity of the hydrogen atoms attached to the alpha carbon both of these effects are due to the ability of oxygen to accommodate the negative charge the typical reactions of aldehydes and ketones are nucleophilic addition reactions before we examine the different types of nucleophilic addition reactions that is first understand the general mechanism of nucleophilic addition reactions the first step is a slow or the rate determining step which involves the attack of a nucleophile on the electron deficient carbonyl carbon since the carbonyl group is flat it is liable to be attacked from above or below the plane our carbon atom as the nucleophile forms a bond with the sp2 plane our carbonyl carbon atom the electron pair of the carbon to oxygen PI bond shifts to the carbonyl oxygen the carbonyl oxygen easily accommodates the electron pair to produce a tetrahedral sp3 alkoxide ion intermediate in the second step the alkoxide ion captures a proton from the reaction medium to give an electrically neutral tetrahedral product if the nucleophile is strong it will readily attack the carbonyl carbon the resulting addition product can be readily protonated by the solvent or by the added acid however if the nucleophile is weak then it requires an acid catalyst to make the nucleophilic addition reaction occur at a reasonable rate the acid protonates the carbonyl oxygen to produce an oxonium ion the oxonium ion is highly reactive towards nucleophilic attack at the carbonyl carbon atom this is because the carbonyl carbon atom carries more positive charge than it does in the unprotonated compound the addition of alcohol to the carbonyl group is an example of acid catalyzed nucleophilic addition the reactivity of the carbonyl group towards nucleophilic addition depends mainly upon the magnitude of the positive charge on the carbonyl carbon that is the electronics factor and the extent of crowding around the carbonyl carbon atom in the transition state that is the static site based on these factors the order of reactivity is formaldehyde without any alkyl group is more reactive than other aldehydes with one alkyl group which in turn a more reactive than ketones that contain two alkyl groups [Music] electronically alkyl groups are electron releasing groups that release electrons and stabilize the carbonyl carbon by reducing the magnitude of positive charge on it hence the electrophilicity on the carbonyl carbon and therefore the reactivity decreases with an increase in the number of alkyl groups [Music] statically the presence of bulky alkyl groups and ketones hinders the approach of the nucleophile towards the carbonyl carbon hence the bulkier the alkyl group the lesser is the reactivity therefore the decreasing order of the reactivity of ketones is acetone is more reactive than a tiny tiny ketone which is more reactive than isopropyl methyl ketone meet high tertiary butyl ketone an AI group has an electron-withdrawing inductive effect so it is expected to destabilize the reactant and speed up the reaction however it seems to stabilize the reactant even more by resonance and does decreases the reactivity dance propanol is more reactive than been salty height because the polarity of the carbonyl group is reduced in benzaldehyde as shown now let us look at some important examples of nucleophilic addition on the carbonyl group [Music] these include addition of hydrogen cyanide addition of sodium bisulfite addition of grignard reagent addition of alcohols addition of ammonia and its derivatives when hydrogen cyanide is added to the carbonyl group of aldehydes and ketones it eats compounds known as sino hydrants as HCN is a very weak acid it is a poor source of cyanide ions hence addition takes place very slowly therefore the addition of a base can generate cyanide ions from the weak acid HCN causing a dramatic increase in the rate of the reaction the cyanide ions being stronger nucleophiles rapidly attack the carbonyl carbon to produce the corresponding sino hydrants sigh no hydrants are useful intermediates in organic synthesis they undergo hydrolysis to ield alpha hydroxy acids or unsaturated acids for example the addition of HCN to acetaldehyde yields acetaldehyde sino hydrogen which on hydrolysis ills lactic acid or alpha hydroxy propanoic acid let's look at the addition of sodium bisulfite when sodium bisulfite is added to an aldehyde or a ketone in the presence of ethanol it gives a water-soluble solid adduct this sonnet and art is filtered from ethanolic solution and then decomposed by an acid or obese to regenerate the carbonyl compound hence this reaction is used for the purification and separation of carbonyl compounds for example acetaldehyde reacts with the saturated solution of sodium bisulfite to give a white crystalline precipitate of acetaldehyde sodium bisulfite yet another addition reaction is the addition of a grignard reagent to the carbonyl group in the Sanditon reaction when a click not reagent rmgx is added to the carbonyl group with its organic group are being attached to the carbonyl carbon and magnesium to the carbonyl oxygen it produces an addition compound which on hydrolysis yields and alcohol as you can see formaldehyde produces a primary alcohol a secondary alcohol with the other aldehydes and tertiary alcohols with ketones this relationship arises directly from our definitions of aldehydes and ketones and our definitions of primary secondary and tertiary alcohols aldehyde reacts with alcohol in the presence of anhydrous hydrogen chloride to form an unstable intermediate known as hemiacetal hemiacetal further reacts with one more molecule of alcohol to give a gem dye alkoxy compound known as acetone this reaction is an example of acid-catalyzed nucleophilic addition in which dry HCl gas protonates the oxygen of the carbonyl group so that the oxonium cation formed is more susceptible to nucleophilic attacks all steps involved in the formation of acetyls from an aldehyde are reversible Keeton's react with an excess of ethylene glycol under similar conditions to form cyclic product known as ethylene glycol kettles buthe acetyls and kettles can be rapidly hydrolyzed with aqueous mineral acids even at room temperature into aldehydes and ketones respectively let's now look at the addition of ammonia and its derivatives when ukyo fights such as ammonia and its derivatives n h2 G are added to the carbonyl group in the presence of acid they form compounds with carbon to nitrogen double bonds known as I mines let's understand the mechanism of this reaction 1 initially the hydrogen ion from the acid attaches itself to the carbonyl oxygen to produce an oxonium cation - this is followed by a nucleophilic attack by the basic nitrogen on the carbonyl carbon to form an intermediate addition product three further the elimination of the water molecule from the intermediate results in the formation of the product with a carbon to nitrogen double bond [Music] since these reactions involved the addition of a nucleophile in the presence of an acid followed by the elimination of the water molecule they are termed as nucleophilic addition elimination reactions aldehydes and ketones react with ammonia derivatives with the general formula in h2g here G is equal to our alkyl group who each in each two in each c6h5 in each Co n h2 etc aldehydes and ketones react with primary air mines to form substituted I mines a ship's base aldehydes and ketones react with hydroxyl air mine to form the corresponding oxides for example acetaldehyde and acetone react with hydroxyl amine to form acetyl doc sign and acetic sign respectively aldehydes and ketones react with hydrazine in H 2 and H 2 and its derivatives such as phenol hydrazine - for dye nitro phenol hydrazine and semi carbon to form the corresponding hydrazone for example acetaldehyde and acetone react with hydrazine to form acetaldehyde hydro-zone and acetone hydro-zone respectively similarly they react with hydrazine derivatives and form the corresponding hydrazone as shown in the equations here hydro zones are usually insoluble solids with sharp melting points moreover op signs & hydras owns went refluxed with dilute hydrochloric acid regenerate the parent aldehyde and ketone hence box signs and hydrazone are used for the detection and purification organic compounds that contain the carboxylic functional group COOH are called carboxylic acids the name carboxyl is derived from the carbonyl group C double bond o and the hydroxyl group ooh each of which it is composed carboxylic acids are widespread in nature I am embers of aliphatic carboxylic acids known as fatty acids our important components of the biomolecules such as lipids fats and oils aliphatic carboxylic acids have been known for a long time a large number of them are known by the common names that refer to their sources rather than to their chemical structures a common names for carboxylic acids are usually derived from Latin or Greek words that indicate the original source of the individual acid all common names of these acids end with IC acid for example the name formic acid each COOH is derived from the Latin word Formica which means red ants why acetic acid ch3cooh is derived from the Latin word a Seton which means vinegar similarly butyric acid is derived from the latin word beautiful which means butter the name caproic acid which is obtained from goat fat is the right from the latin word caper which means goat a dicarboxylic acid contains two carboxyl groups the table here gives the common names of some dicarboxylic acids the names can be easily remembered by the mnemonic o'mike such good apple when it comes to substituted acids the position of the substituent is indicated by the Greek letters alpha betta gamma etc the carbon adjacent to the carboxylic is assigned the letter alpha the mixed carbon betta the next one gamma and so on for example two methyl groups substituted on the alpha and beta carbons in a six carbon carboxylic acid is named alpha beta dimethyl Caprio ik acid aromatic acids are named as the derivatives of benzoic acid c6h5 COOH [Music] for example compounds a and B shown here an INT patter bromo benzoic acid and auto parody nitro benzoic acid respectively methyl benzoic acid are given the special names of choleric acids for example the compound shown here is named mettaton looook acid now let's look at the IUPAC system in the IUPAC system carboxylic acids are named by replacing the ending e of the corresponding alkane by oh I see acid to form Alka Noack acid for example the IUPAC name for carboxylic acid containing one carbon is methanoic acid obtained by replacing the ending II of methane by oh I see acid similarly carboxylic acids containing two three and four carbon atoms are named ethanoic acid propanoic acid and butanoic acid respectively by replacing the ending II of the alkanes concerned by oh I see acid blaming the higher numbers the longer string containing the carboxyl group is selected and numbering is done from the side of the carboxyl group always giving it the number one for example the compound shown here is named for methyl hexanoic acid for naming compounds containing more than one carboxyl group the ending II of the alkene is retained and the multiplicative prefix die try etc is added to the term I Cassatt the position of the COOH groups are indicated by Arabic numeral before the multiplicative prefix for example the compound shown here which contains three carboxyl groups on the first second and third carbons is named propane one two three tri carboxylic acid in the IUPAC system benzoic acid is named benzene carboxylic acid note here that the common name benzoic acid is also accepted as the IUPAC name if side chains or substituent's are present then they are indicated by numbers with a carboxyl carbon atom being numbered one for example penile acetic acid shown here is named two phenyl ethanoic acid similarly phthalic acid is named benzene one two dicarboxylic acid the name of a salt of carboxylic acid consists of the name of the cation followed by the name of the acid with the ending I see acid being changed to eight for example the compounds given here are named ammonium formate and potassium 2/3 die bromo propionate respectively carboxylic acids can be prepared by several different methods oxidation of primary alcohols and carbonyl compounds oxidation of alkyl benzene combination of grignard reagents hydrolysis of nitriles hydrolysis of a Kyle or lines and an hydrates hydrolysis of esters let us see how carboxylic acids can be prepared from primary alcohols and carbonyl compounds primary alcohols or aldehydes on oxidation with oxidizing agents such as acidified or alkaline potassium permanganate acidified potassium dichromate or chromium trioxide in sulfuric acid gives carboxylic acids with the same number of carbon atoms for example 2-methylbutane one all on oxidation with acidified or alkaline potassium permanganate gives to me type butanoic acid aldehydes can also be oxidized to the corresponding carboxylic acids even with mild oxidizing agents such as tollens reagent or Fehlings reagent example aldehyde is oxidized to acetic acid in the presence of tollens or Fehlings reagent ketones also give carboxylic acids on oxidation however ketones are oxidized only under vigorous conditions such as strong oxidizing agents and elevated temperatures under these conditions ketones form a mixture of carboxylic acids with a fewer number of carbon atoms as shown here for example butanone on oxidation with hard to concentrated nitric acid gives a mixture of propanoic acid and methanoic acid one of the most useful methods of preparing an aromatic carboxylic acid is the oxidation of an alkyl benzene chromic acid or acidic or alkaline potassium permanganate is generally used for this purpose it must be noted that irrespective of the length of the sidechain the alkyl group is entirely oxidized into a carboxyl group for example tahleen or Etha benzene on oxidation with acidic potassium permanganate gives benzoic acid it is important to note that only primary and secondary alkyl groups are oxidized into a c oo each group while tertiary alkyl groups remain unaffected for example n-propyl benzene and isopropyl benzene are oxidized to benzoic acid in the presence of chromic acid or acidic or alkaline potassium permanganate while tertiary duty benzene undergoes no change under these conditions in the presence of these oxidizing agents even suitably substituted alkenes are oxidized to carboxylic acids for example Butte to in on oxidation in the presence of acidified potassium permanganate gives ethanoic acid cycloalkanes on the other hand oxidized to dye weak acids under these conditions for example cyclohexene with acidified potassium permanganate undergoes oxidation to adipic acid or hexane one six dioic acid the combination of grignard reagents is another important method for the preparation of carboxylic acids grignard reagents react with carbon dioxide to form the magnesium salts of carboxylic acids the free asset can be obtained from the salt by treating it with mineral acids great not reagents can be obtained by the reaction of alkyl halides with magnesium metal in dry ether the conversion of tri methyl acetic acid from tertiary butyl chloride is illustrated here did you notice that the acid formed by this method contains one more carbon atom than the Alka highlight does this method has the special advantage of increasing the length of a carbon chain hydrolysis of nitriles is another method for preparing the carboxylic acids nitriles on boiling with aqueous alkali or acid get hydrolyzed to the respective carboxylic acids aliphatic nitriles can be prepared by treating an alkyl halide with sodium cyanide in the presence of the solvent dimethyl sulfone site the synthesis of pentanoic acid from n butyl bromide shown here illustrates the complete method note that the assets produced from the alkyl halide also contain one carbon atom more than the original alkyl halide the hydrolysis of acid derivatives such as air mines acid chlorides and hydrants and esters eels carboxylic acids amides undergo hydrolysis and being buoyed with a dilute acid or alkali hydrolysis eels carboxylic acid and an ammonium salt with an acid and carboxylic acid and ammonia with an alkali for example acetamide on being boiled with dilute HCl undergoes hydrolysis to give acetic acid and ammonium chloride on the other hand when it is boiled with aqueous sodium hydroxide it gives sodium acetate and ammonia acid chlorides on hydrolysis give carboxylic acids for example acetyl chloride policies in presence of water gives acetic acid and hydrochloric acid the hydrolysis of acid chlorides are curse readily in presence of an alkali hydrolysis in the presence of an alkali first eels carboxylate ions which on acidification give the corresponding carboxylic acids for example when acetyl chloride is hydrolyzed with an alkali it first yields acetate ions which give acetic acid on acidification and hydrants give the corresponding acids on hydrolysis for example acetic anhydride gives acetic acid acid hydrolysis of esters directly gives the carboxylic acids concerned for example ethyl acetate on boiling with a dilute acid gives acetic acid and eath high alcohol alkaline hydrolysis of esters on the other hand first results in the formation of carboxylates which on acidification gives the corresponding carboxylic acid for example on boiling with aqueous sodium hydroxide ethyl benzoate gives sodium benzoate and etai alcohol a certification of sodium benzoate gives benzoic acid having learned the different methods of preparation of carboxylic acids now try to accomplish the following transformations Benson key right into phenol acetic acid or to promote a lean into Auto bromo benzoic acid tersh repent I'll go right in to eat I'll dimethyl acetic acid the conversion of benzine flow right into phenol acetic acid involves an increase of one carbon atom the conversion can be achieved by first treating benzene fluorite with sodium cyanide to eat Sinai acetone I trial followed by hydrolysis with aqueous acid this is a simple reaction of oxidation of the alkyl group this can be achieved by the oxidation of auto bromo tahleen in the presence of alkaline potassium permanganate the conversion of tertiary pentafluoride into eat i'll dimethyl acetic acid also involves an increase in the carbon chain this can be achieved by first treating the tertiary pentachloride with magnesium to eat the corresponding grignard reagent the grignard reagent on reaction with carbon dioxide followed by acid hydrolysis gives etai dimethyl acetic acid let us begin with the physical states of carboxylic acids the first nine members that is C 1 to C 9 of aliphatic carboxylic acids are colorless liquids with sharp or disagreeable odors higher members are wax like solids and are almost odorless due to their low volatility coming to solubility in water the first four members of carboxylic acids are fairly soluble in water due to the ability of the carboxyl group to form hydrogen bonds with water molecules their solubility decreases with the increase in the length of the carbon chain higher carboxylic acids are virtually insoluble in water due to the greater influence of the hydrocarbon part the simplest aromatic acid benzoic acid contains too many carbon atoms to show any appreciable solubility in water carboxylic acids are soluble in less polar solvents like ether alcohol and benzine let's now discuss the boiling points of carboxylic acids the boiling points of carboxylic acids are higher than that of aldehydes ketones and alcohols of compatible molecular weights for example although acetic acid and n-propyl alcohol have the same molecular weight acidic acid has a boiling point of 118 degrees centigrate y Enpro pi alcohol has a boiling point of 97 degrees centigrade this is due to the extensive association of carboxylic acid molecules through intermolecular hydrogen bonding the hydrogen bonds are not broken completely even in the vapor phase that is why most carboxylic acid exists as dimers in the vapor phase or in a protic solvents let us now look at the acidity of carboxylic acids the most characteristic property of carboxylic acids is the one that gives them their name acidity just like alcohols carboxylic acids react with electropositive metals like sodium and liberate hydrogen gas unlike phenols carboxylic acids react even with weaker basis such as carbonates and bicarbonates to form the corresponding salts with the evolution of carbon dioxide the reaction of carboxylic acids with weak bases clearly proves that they are tremendously more acidic than the very weak organic acids alcohol's and acetylene hence the reaction of carboxylic acids with carbonates and bicarbonates is used to detect the presence of the carboxyl group in an organic compound carboxylic acids are much stronger at since than water in an aqueous solution a carboxylic acid exists in equilibrium with the carboxylate and ion and the hydronium ion only equation here as for any equilibrium the concentrations of the components are related by the expression K EQ is equal to the product of the concentrations of RC o OH - and h3o plus divided by the product of the concentrations of h2o and RC o o H since the concentration of water remains almost constant we can combine it with keq to obtain the expression ke is equal to ke Q multiplied by the concentration of h2o is equal to the product of the concentrations of RC o o minus and h3o plus / the concentration of our COOH here keq is the equilibrium constant and ke which is equal to ke Q multiplied by the concentration of h2o is called the acid dissociation constant every carboxylic acid has its characteristic ke which indicates how strong an acid is the larger the value of ke the greater is the extent of ionization and therefore the stronger is the acid for example among the unsubstituted mono carboxylic acids formic acid with the highest value of ke is the strongest the values of ka are usually very small hence for convenience they are often coated in logarithmic form as PKA is equal to negative log ka most PKA values fall within the range of 1 to 14 the smaller the pKa the stronger is the acid for example among tri fluoro acetic acid with a pKa value of 0.23 benzoic acid with a pKa value of 4 point one nine and acetic acid with a pKa value of four point seven six tri fluoro acetic acid with the lowest PKA value is the strongest organic acid stronger acids has PKA values less than 1 for example trifluoroacetic acid with the pKa value of 0.23 and trichloroacetic acid with a pKa value of 0.65 are strong acids assets with PKA values between one and five are considered moderately strong for example floral acetic acid with a pKa value of two point six six Lauro acetic acid with a pKa value of 2.86 a nitrile acetic acid with pKa value of 1.68 our more tricky acidic acids weak acids has PKA values between 5 and 15 for example fennel with a pKa value of nine point nine five or to christen and with a pka value of 10.28 are weak acids extremely weak acids have pKa values greater than 16 for example ethanol with the pke value of 16.0 and acetylene with a pKa value of twenty three point zero are extremely weak acids carboxylic acids are acidic and readily lose a proton because the carboxylate ion formed by ionization all reaction with the base is stabilized by resonance according to the resonance theory the carboxylate ion is a hybrid of two structures which being of equal stability contribute equally the negative charge is evenly distributed over the two oxygen atoms let's now compare the acidity of carboxylic acids with the acidity of phenol when you compare the resonance structures of the carboxylate ion and the phenoxide ion you can clearly see that the carboxylate ion is stabilized by two equivalent resonance structures in which the negative charge is on the more electronegative oxygen atom the phenoxide ion on the other hand has non equivalent resonance structures in which the negative charge is on the less electronegative carbon atom hence resonance is more important in the carboxylate ion than in the phenoxide ion furthermore the carboxylate ion is more resonance stabilized than is the phenoxide ion this is because a negative charge is more effectively dispersed over two electronegative oxygen atoms in carboxylate ions less so over one oxygen atom and the less electronegative carbon atoms is phenol site thus carboxylic acids are more acidic than phenols let us now examine the effect of substitutes on the acidity of carboxylic acids electron-withdrawing groups increase the acidity of carboxylic acids by stabilizing the anion through the dispersal of the negative charge on the carboxylate ion by the inductor all resonance effects for example chloro acetic acid with the electron withdrawing chlorine group is a hundred times as strong as acetic acid the acidity of carboxylic acids increases with an increase in the number of electron withdrawing groups for example trichloroacetic acid with three electron withdrawing groups is more acidic than dichloro acetic acid with two electron withdrawing groups which in turn is more acidic than Manu chloro acetic acid with one electron withdrawing group the strength of the electron withdrawing substituent determines the magnitude of the effect on acidity for example fluoro acetic acid is stronger than chloro acetic acid which in turn is stronger than bromo and iodo acetic acid this is in accordance with the decrease in the electronegativities of halogen atoms the knew that electron withdrawing group the greater is the acidity of carboxylic acid for example among the hallo substituted acids shown here alpha plural butyric acid with the chlorine atom on the alpha carbon is more acidic than beta which in turn is more acidic than gamma chloro butyric acid the increasing order of acidity of some of the electron withdrawing groups is as shown here note that in the case of carboxylic acids in which the finai overnight group is directly attached to the carboxyl group the listen increase in the acidity of carboxylic acid instead of the decrease expected due to the resonance this is because of the fact that the carboxyl group is attached to a more electronegative sp2 hybridized carbon electron donating groups on the other hand decrease the acidity by destabilizing the anion by intensifying the negative charge thus among the unsubstituted aliphatic mono carboxylic acids formic acid with no alkyl group is about ten times stronger than acetic acid which in turn is stronger than propionic acid and so on in the aromatic carboxylic acids too electron-withdrawing groups increase the acidity why electron donating groups decrease it for example badda Nitro benzoic acid with an electron-withdrawing group is more acidic than benzoic acid which in turn is more acidic than Padme Toxie benzoic acid with an electron donating group the chemical properties of carboxylic acids can be conveniently studied under five headings reactions involving the hydrogen atom of the COOH group reactions involving the Oh each part of the COOH group reactions involving the COOH group as a whole reactions involving the alkyl group of the acid reactions involving the Ave group in aromatic acids let us examine the reactions involving the hydrogen atom of the COOH group first you already know that molar carboxylic acids evolved hydrogen which strongly electropositive metals such as sodium potassium and Kashyap and forms salts with alkyl e's this reaction essentially involves the hydrogen atom of the COOH group the reaction of formic acid with sodium metal and sodium hydroxide is shown here note that although the salt sodium formate is formed in both the reactions nitrogen gas is evolved only in the reaction with sodium Moeller carboxylic acids being stronger than phenols react with weaker basis such as carbonates and bicarbonates to form the corresponding salts with the evolution of carbon dioxide this reaction is used to detect the presence of a carboxyl group in an organic compound for example in the two test tubes shown here test tube a contains acetic acid and test tube B contains sin on when sodium bicarbonate is added to both the test tubes you can see that a further sense is observed only in test tube II and not in test tube be the reaction of acetic acid with sodium bicarbonate is shown here does this reaction can be used as an identification test for the carboxyl group now let's examine the reactions involving the hydroxyl group the hydroxyl group in carboxylic acids behaves like alcohols and can be easily replaced by groups such as Oh cor who are in h2 or CL to form and hydrides esters amides and acid chlorides respectively let's look at each of these reactions in detail on being heated with a dehydrating agent such as phosphorus pentoxide or with mineral acids such as sulfuric acid carboxylic acids give the corresponding anhydride for example acetic acid on heating with phosphorus pentoxide loses a water molecule to form acetic anhydride you carboxylic acids react with alcohols in the presence of a mineral acid catalyst such as concentrated sulfuric acid or dry hydrochloric acid gas to form reaction is reversible in nature and is known as esterification for example acidic acid reacts with ethyl alcohol in the presence of concentrated sulfuric acid to form Etha acetate the esterification of carboxylic acids with alcohols is a nucleophilic acyl substitution reaction the steps involved in the mechanism are the first step is the protonation of the carbonyl group in the presence of mineral acids the carbonyl group of the carboxylic acid accepts a proton to form a protonated carboxylic acid as shown here the second step is the nucleophilic attack by the alcohol molecule due to the protonation the carbonyl carbon becomes more electrophilic and is therefore attacked easily by the electron rich oxygen atom of the alcohol molecule to form a tetrahedral intermediate the third step is the loss of the water molecule proton transfer in the tetrahedral intermediate converts the hydroxyl group into an h2o plus group which being a better leaving group is lost as a water molecule the result of this step is a protonated ester the last step is the loss of the proton the protonated ester thus formed finally loses a proton to give the ester the o-h group of carboxylic acids is replaced by a chlorine atom on being treated with phosphorus halides of--the ionized chloride to form acid chlorides the reactions of acetic acid with phosphorus trichloride phosphorus pentachloride or thionyl chloride are shown here that although acetyl chloride is the main product in all the three reactions the byproducts vary pionen chloride is preferred because both the byproducts sulfur dioxide and hydrogen chloride being gases escape the reaction mixture making the purification of the products easier carboxylic acids when treated with ammonia form ammonium salts which upon heating lose the water molecule and forms amides example acetic acid reacts with ammonia to form ammonium acetate on being heated this ammonium acetate loses a water molecule to form a satellite similarly a dicarboxylic acid such as talaq acid forms ammonium callate on reacting with ammonia on heating ammonia tallit loses two water molecules to form phthalimide when the stand amide is heated further it loses an ammonia molecule to give talam ID as the final product let's look at the reactions involving the COOH group as a whole the first one is the reduction of the carboxyl group carboxylic acids on reduction with lithium aluminium hydride or diborane gives primary alcohols for example acetic acid on production with lithium aluminium hydride gives a high alcohol you the second one is the decarboxylation reaction sodium salts of carboxylic acids when heated with soda lime loses carbon dioxide to form hydrocarbons this reaction is known as decarboxylation for example sodium acetate when heated with soda lime gives meeting Cold's electrolysis of sodium or potassium salt of carboxylic acids give hydrocarbons with twice the number of carbon atoms present in the alkyl group of the acid example the electrolysis of a concentrated aqueous solution of sodium acetate gives ethene at the anode the other set of reactions are the reactions of the al-qaida group carboxylic acids with an alpha hydrogen react with chlorine or bromine in the presence of a small amount of red phosphorus to give alpha hallow carboxylic acids this reaction is known as hell volha Solinsky reaction for example propionic acid on reaction with chlorine in the presence of red phosphorus gives Alfa chloro propionic acid finally the reactions involved in the aryl group in aromatic carboxylic acids aromatic carboxylic acids undergo the usual electrophilic substitution reactions of the benzene drink such as nitration and sulfonation the CEO each group a meta directing group directs the incoming electrophile to the meta position furthermore as it is a deactivating group reactions occur only under drastic conditions example benzoic acid on eating with the mixture of concentrated nitric acid and concentrated sulfuric acid gives meta nitrobenzene it is important to note that carboxylic acids do not undergo the friedel-crafts reaction because the carboxyl group is deactivating and the catalyst aluminum chloride which is a Lewis acid gets bonded to the carboxyl group strongly let's see the important uses of carboxylic acids methanoic acid is used as a coagulating agent for latex in the rubber industry it is used as an acid bath in the textile dyeing and electroplating industries it is used for the dehydration of Heinz in the leather industry ethnic acid is used as solvent and as vinegar in the food industry it is also used in the manufacture of plastics and rayon hexane 1 6 dioic acid or adipic acid is used in the manufacture of nylon 66 esters of benzoic acid are used in perfumery sodium benzoate is used as a food preservative for fruit jams and juices in the food industry hiya fatty acids are used for the manufacture of soaps and detergents you [Music] [Applause] [Music] [Applause] [Music] [Applause] [Music] you