hey guys welcome to igcc study Budd where you can revise chemistry topics from the Cambridge igcs syllabus if you are enjoying our videos so far please don't forget to hit the like button and subscribe to our channel in this video you are going to learn part one of topic 11 organic chemistry or organic chemistry is the study of compounds that contain carbon these compounds are called organic compounds and are commonly found in living organisms though they can also be synthesized artificially many organic compounds are hydrocarbons which are made up of only hydrogen and carbon atoms organic compounds can be represented in different ways displayed formula structural formula and general formula the displayed formula shows every atom and bond in the molecule giving a clear picture of how the atoms are connected let's use the compound butane c4h10 as an example butane has four carbon atoms and 10 hydrogen atoms each line between atoms represent a single calent Bond carbon atoms are arranged in a straight chain with each carbon forming single bonds to four other atoms usually hydrogen because carbon needs four bonds to be stable carbon has a veency of four for the end carbon atoms each is bonded to one carbon atom and three hydrogen atoms for the middle carbon atoms each is bonded to two carbon atoms and two hydrogen atoms so the displayed formula gives a clear picture of how the atoms are arranged and connected showing every atom and Bond explicitly next what is a structural formula a structural formula is an unambiguous or clear way of describing how the atoms in a molecule are arranged showing the order in which they are bonded together for example the structural formula of ethine shows two carbon atoms double bonded to each each other with each carbon atom bonded to two hydrogen atoms the structural formula of ethanol shows a two carbon chain where the first carbon is bonded to three hydrogens and the second carbon is bonded to two hydrogens and an O group the structural formula of methyl ethano shows a methyl group bonded to a carbony group and an oxygen atom which is also bonded to another methyl group this clear structure helps understand the molecules shape and bonding so the structural formula is a simplified way to show the arrangement of atoms focusing on how the atoms are bonded together without showing every single Bond with reference to our previous example the structural formula of butane simplifies the displayed version showing the key bonds between atoms like this ch3 ch2 ch2 and ch3 this focuses on the carbon chain and groups without displaying all individual bonds the general formula is a way to represent a family of organic compounds using a pattern that fits all members of that group or homologous series example for the alkan family butane follows the general formula CN h2n +2 in organic chemistry n in a general formula typically represents the number of carbon atoms in a molecule within a homologous series for butane n is equal to 4 so the general formula becomes C4 h10 we will learn about this in more detail shortly once again organic compounds can be represented in different ways displayed formula structural formula and general formul formula by using these formulas we can better understand and represent the structure and behavior of organic compounds let's learn some terminology to understand organic chemistry better a functional group is an atom or a group of atoms within a molecule that determines or decides the chemical properties and reactions of a homologous series that is a group of compounds with similar structures and properties for example alkanes have single carboncarbon bonds and no specific functional group alkenes have a carboncarbon double bond which is the functional group alcohols have a hydroxy group as the functional group carboxilic acids have a carboxy group as their functional group each functional group gives the molecules in that series their characteristic chemical behavior for example in alcohols the hydroxy group is the functional group that defines their properties and reactions what is a homologous series a homologous series is a family of similar compounds that have similar chemical properties because they contain the same functional group so for example in this case the general formula is CN h2n +1 o which applies to all alcohols in this family the functional group is The O Part and the homologous series is the family to which the this general formula belongs the family of alcohols the general characteristics of a homologous series are having the same functional group all compounds in the series contain the same functional group which determines their chemical properties having the same general formula each compound in the series follows the same general formula such as CN h2n +2 for alkanes differing from one member to the next by a ch2 unit each successive compound differs by a single ch2 group making the series uniform in structure displaying a trend in physical properties physical properties such as the boiling point or melting point show a gradual change as you move through the series sharing similar chemical properties all compounds in the homologous series react in similar ways due to their shared functional group now that you know the terminology let's dive further into the general formulas and interpretations for the compounds in the same homologous series The General formul formula of alkanes is CN h2n +2 a saturated compound has molecules in which all carboncarbon bonds are single bonds alkanes are saturated hydrocarbons meaning they contain only single bonds between carbon atoms for every n carbon atom there are 2 N +2 hydrogen atoms example for methane where n is equal to 1 there is one carbon atom the number of hydrogen atoms is calculated as 2 n + 2 so that is 2 * 1 + 2 is equal to four hydrogen atoms so methane is CH4 the general formula of alkenes is cnh h2n an unsaturated compound has molecules in which one or more carboncarbon bonds are not single bonds so alkenes are unsaturated hydrocarbons that contain at least one carbon carbon double bond for every n carbon atom there are two n hydrogen atoms example for athine where n is equal to 2 there are two two carbon atoms the number of hydrogen atoms is calculated as 2 N that is 2 * 2 is equal to 4 hydrogen atoms so ethine is C2 H4 the general formula of alcohols is CN h2n +1 o alcohols contain an O group called The hydroxy group for every n carbon atoms there are 2 n + 1 hydrogen atoms plus one hydroxy group example for ethanol where n is equal to 2 there are two carbon atoms the number of hydrogen atoms is calculated as 2 n + 1 so that is 2 * 2 + 1 equal to 5 hydrogen atoms so ethanol is C2 H5 o the general formula of carboxilic acids is CN h2n +1 Co carboxilic acids container Co or carboxy group for every n carbon atoms there are 2 n + 1 hydrogen atoms plus one carboxy group example for ethanol OIC acid where n is equal to 1 there is one carbon atom the number of hydrogen atoms is calculated as 2 n + 1 that is 2 * 1 + 1 giving three hydrogen atoms so ethanoic acid is ch3 co therefore each general formula follows a specific pattern that fits all compounds in its homologous series finally let's look at structural isomers remember we learned that a structural formula clearly shows how the atoms in a molecule are arranged and how they are bonded together sometimes a single molecular formula can have more than one structural formula they are called structural isomers structural isomers are compounds that have the same molecular formula but different structural formula meaning the atoms are arranged differently within the molecule for example the molecular formula c4h10 can represent two different compounds that is C4 h10 can exist as two structural isomers one is like this a straight chain structure and the other is like this a branched structure where a methyl group is attached to the second carbon buttine also has structural isomers one buttin and two buttin as you may notice the double bonds are at different places in both even though the molecular formula is the same the different Arrangements lead to distinct structures and properties that concludes part one of topic 11 organic chemistry are you enjoying our videos are they helping you here's a way you can show your appreciation and support our continued efforts you may use YouTube super thanks to send us thanks hope this video helped you please share your thoughts in the comment section be sure to check out our other videos from our playlists thank you for watching and please don't forget to subscribe to igcs study budy for more revision videos bye