hello everybody my name is iman welcome back to my youtube channel today we're going to continue our mcat organic chemistry practice and today we're going to talk about alcohols so i have a couple questions about and relating to alcohols we're going to work through them i'm going to give you the background information you need to solve each one and if you've forgotten some details here and there i will point you to some of the videos i have in my opin102 playlist for you to review if you need it awesome let's jump in problem one alcohols have higher boiling points than their analogous hydrocarbons because blink a the oxygen atom and alcohols have shorter bond lengths b hydrogen bonding is present in alcohols c alcohols are more acidic than their analogous hydrocarbons or d alcohols can be oxidized to ketones so there's three important trends to consider when we're talking about boiling points and um these three things are one the relative strength of the four intramolecular intermolecular forces that's your ionic your hydrogen bonding your dipole dipole and van der waals dispersion forces these influence attractive forces and they influence boiling points two boiling points increase as the number of carbons is increased and three branching decreases boiling points now alcohols have higher boiling points than your hydrocarbons because of their polarized oxygen hydrogen bonds so here's a water all right your your oxygen is going to be partially negatively charged and your hydrogen is going to be partially positively charged so this bond is um inherently polarized right now oxygen of one molecule can be attracted to the hydrogen of another water molecule and the hydrogen of one water molecule can be attracted to the oxygen of another water molecule all right what's happening here is what's called hydrogen bonding and this hydrogen bonding is um an attractive force and heat is used to overcome these bonds to to break off these intermolecular bonds and so this is inherently going to cause higher boiling points so the hydrogen bonding that is present in alcohols is one of the reasons why they have higher boiling points than hydrocarbons this is not a problem or an issue with hydrocarbons they don't hydrogen bond to other hydrocarbons all right so the answer is going to be b fantastic now number two says tertiary alcohols are oxidized with difficulty because why so tertiary alcohols can be oxidized but only under like super extreme conditions because their substrate carbon doesn't have any spare hydrogens to give up and one of the reasons one of the ways that we can um oxidize alcohols is when that carbon attached to the oxygen and the alcohol is primary or secondary and there's hydrogens to spare so that oxidation can occur when there's a tertiary alcohol that carbon that's attached to the alcohol all right has no hydrogens to give to donate so that we can oxidize this bond and form a double bond for example so the answer here is that there are no hydrogens attached to the carbon with the hydroxyl group so that oxidation can occur now just also as a as a segway into reminders of reduction in oxidation there are kind of like three definitions that are associated with reduction in oxidation and you kind of get introduced to the first definition in general chemistry and then a few other variations of the way that we define oxidation and reduction in organic chemistry but there's these three points these three definitions for each reduction in oxidation i think are important to know so reduction of some form of gain of electrons or formation of a carbon hydrogen bond or a loss of a carbon oxygen bond whereas oxidation you think of it as a loss of electron a loss of a carbon hydrogen bond or a formation of a carbon oxygen bond or things that are equivalent to that like a carbon nitrogen bond or so on and so forth so keep these definitions in mind as we continue some of these practice problems because it might reappear all right awesome now number three here says the iupac name of this molecule is blink so we're just gonna go through our normal nomenclature rules here and work this out so first longest carbon chain let's find that one two three three carbons here all right so the three carbon's parent name is propane awesome now do we have any modifiers so any functional groups that might change the parent name and yes we do we actually haven't we have alcohol and not just any alcohol but two alcohols all right now what do we do when we have one alcohol the end of the parent name changes to all ol now we have two alcohols here so our ending of our parent chain is actually going to be changed to die old to notify that we actually have two alcohols all right do we have any substituents besides the alcohols not really so we don't really have to worry about this now numbering all right we want to number this in a way that gives substituents the least amount of numbers so if we number here one two three our substituents get number one and two for the alcohols or the modifiers i should say if we number the other way all right it's not efficient but i'll show you if we number it the other way one two three then our substituents are at two and three that's not what we're looking for we're looking for the lowest numbers associated with groups attached to our parent chain alright so our alcohols are at one two diol awesome now that's the numbering fantastic now we could put it all together all right we can do one two pro pen deal or we can do propane one two dial both of these work and one of these is present in our answer choices and that's obviously going to be b fantastic let's do another nomenclature problem the iupac name of this molecule is blank all right so what is our longest parent chain we can say well this molecule actually has a common name a part of this molecule has a common name that we're aware of and this is one of the common names for um for like benzene rings that we covered in chapter i want to say 18 or 19 o chem 2 um where we talk about uh phenols and common names for uh phenol derivatives if you will so uh or benzene derivatives i'm so sorry now this benzene has an oh group this has a common name we learned and that's finnall so we can keep this common name and we can tell that it's part of some of the options so that might be helpful we're going to keep final as our our our name first step for our naming here all right and then as for substituent we have this one methyl group all right one methyl group and in reference to our phenol right we have here's our um ortho meta and para positions this methyl is in our meta position all right and so if we want to put the name of this together we could do meta or just m methyl phenyl and that is the name of our molecule so we're going to go for b also five which of the following correctly lists methanol isobutyl alcohol and propanol by decreasing boiling points cool so we talked about things that affect our boiling points once again i'm going to tell you the three trends here the relative strength of the four intermolecular forces going from strongest to weakest ionic hydrogen bonding dipole dipole and van der waals dispersion forces these influence boiling points based off of attractive forces going from strongest to weakest here that create higher boiling points to weaker boiling points all right relatively speaking two boiling points increase as the number of carbons is increased and three branching decreases boiling points all right so we're working with 23 here because we're gonna draw each one of these here's methanol here's propanol and here's isobutyl alcohol and what you notice this one has one carbon three carbons and four carbons in addition to a little bit of branching here all right so we're kind of increasing branching increasing in less carbons here and going to higher carbons so that means this molecule has the highest boiling point and this molecule has the lowest so this is our range so highest boiling point is isobutyl alcohol then propanol then methanol our answer choice here is c fantastic six which of the following correctly lists hexanol phenol and cyclohexanol by increasing acidity of the hydroxyl hydrogen all right so i drew all of these out for us your cyclohexanol phenyl and hexanol all right so there's several ways that we can answer this question all right we can um opt for pkas and assign pkas to each one of these and that might help us answer this question or if you've forgotten pkas totally fine we can just go off of reo we can begin to deprotonate each one of these hydrogens in our hydroxyl groups all right and put negative charges here and then go through reo a r i o atom resonance induction and orbitals to try to find which one of these since we've deprotonated is the most stable base all right oreo is going to help us find the most stable base all right most stable base is the most acidic one protonated all right so we can use that kind of trend to help us find the most acidic hydroxy height uh the least acidic hydrogen or or the least um yeah acidic hydroxyl hydrogen to the most acidic hydroxyl hydrogen all right this is like a chapter this is a chapter three concept back in ochem one all right so first letter a for atom which atom bears the negative charge in all three of these it is the oxygen all right so this question doesn't help us narrow our problem down any further we move on to r which which of these participate in resonance easy the phenyl does there is resonance this is a benzene ring so there's double bonds and we can form resonance structures all right so out of these three this is the most stable base which means when it's protonated it's the most acidic alright so this is our most acidic number one cool now we're comparing these two all right we can go to i for induction all right um which which one do they participate in induction so kind of off of this eye what we can say is we can work with this a little bit all right the acidity of what we have left cyclo hexanol and hexanol are actually really close but the hydroxyl hydrogen of hexa f hexanol is slightly more acidic why because the ring structure of cyclohexanol is slightly electron donating all right slightly electron donating which is gonna make this less acidic all right and this group our normal hexanol is going to beat it in terms of acidity and this kind of ties in our i and o concepts here and so this is our second most acidic and this is our third most acidic all right so phenol is the most with the greater sign then hexanol greater and then cyclohexanol answer choice b seven says which of the following will convert this molecule to this molecule i've drawn it out here for you all right here's this first molecule they've given us three carbon with an alcohol at the end we want to convert it to um that alcohol group to a aldehyde okay so very important we're going from what is here a primary alcohol to an aldehyde okay fantastic what do you need when you go from a primary alcohol to an aldehyde all right and i have this little nice table actually to remind us of some of this stuff if we want to go from primary alcohol to aldehyde we need a weak oxidizing agent like pcc or dmp all right this is kind of what we're looking for all right now if you were going from primary alcohol to carboxylic acid then you would need a stroke a strong oxidizing agent like potassium permanganate or high or or chromic acid no we're not trying to get to a carboxylic acid we specifically want that aldehyde so what one of these will do this only pcc these two one and three would take our primary alcohol and actually convert it to a carboxylic acid this is not what we want we simply want aldehyde and so we can only use pcc for this reaction so the answer is b all right a little bit more of these questions which of the following will convert cyclohexanol drawn it here to cyclohexanone all right we've taken this secondary alcohol all right we've converted it to a ketone okay so what kind of agent do we need what kind of oxidizing agent do we need for this well just to quickly touch up if you're starting off with a secondary alcohol trying to go to a ketone you can use a weak or a strong oxidizing agent so actually you can use pcc or dmp or you can use potassium permanganate you can use chromic acid weak or strong both kinds of oxidizing asians will take your secondary alcohol to a ketone so let's look at these options all right chromic some form of chromic acid uh pyridine chlorochromate by the way this is just pcc fantastic dichromate also works all right these two are strong oxidizing agents this is a weak oxidizing agent these all work to convert our secondary alcohol to a ketone so the answer is d now nine successfully converting three phenyl propanol two three phenyl propanoic acid by the john's oxidation requires the oxidizing agent the solvent and what else all right acidic conditions provided by dilu sulfuric acid are required to complete jones oxidation all right and this is this is a nice friendly reminder for you what what is required for a jones oxidation reaction it takes our primary alcohol takes it all the way to a carboxylic acid or if you have a secondary alcohol it will take it to a ketone what you need all right is that sulfuric acid all right you need that dilu sulfuric acid okay so that's going to be a by the way b is base you don't want that all right high temperatures are not required for this and you can definitely have water it is okay so the only right answer choice here is a 10 says trading two methyl one propanol with methyl sulfonyl chloride in base all right that's this protecting group this is a protecting group followed by a reaction with pyridine chlorochromate that's just pcc guys oxidizing agent and a final step in strong acid is going to give us an end product of what this is a trick question all right and it's a trick question especially if you don't remember what methyl sulfur chloride is all right you saw it commonly in just its shortened molecular formula quite a lot in organic chemistry too soc so3 cl this is a protecting group what it does when you treat this first with this protecting group is now your alcohol changes to that protecting group so3 cl then when you treat it with an oxidizing agent absolutely nothing happens okay absolutely nothing happens and then when you treat it with sulfuric acid sulfuric acid is simply going to remove that protecting group and then you get come back you finish this whole reaction off with exactly what you started off with and so the answer is a all right now 11 says here reaction of one phenyl ethenone with ethylene glycol this is your ethanol ethylene glycol here's your one phenyl uh ethanone all right treating it with ethan ethylene glycol also known as ethane 1 2 diol and aqueous sulfuric acid will result in the formation of what so we're starting off with a ketone and what this is here is actually going to be a protecting group when we talked about ketones and aldehydes we talked about how things that have two alcohols at the end here with some hydrocarbon in the middle can act as a protecting group that can form hemi acetyl groups and hemi keto groups all right why what does it have what happens here when we treat it with this protecting group you take this ketone and instead you're kind of forming this hemi keto or hemi acetyl group now since we start with a ketone our ending is a ketole if this was an aldehyde and we were treating it with this protecting group it would be uh acetol all right so it simply acts as a protecting group it lines up with you know here's your here's your um ethylene glycol right here oh h right has two carbons and kind of replaces this double bond you lose that you form this keto group right here fantastic so that is a and now 12 oh this is our last problem treatment of this molecule with chromate under appropriate reaction conditions will yield which of the following molecules all right this is a great question right what do we have here to start off with this is a primary alcohol and we're treating it with this like chromic acid kind of thing that is going to be an oxidizing agent not just any oxidizing agent all right a strong one or anything with chromate is going to be a strong oxidizing agent at least in the limits of organic chemistry class one and two all right so you have a primary alcohol and you have a strong oxidizing agent what is this going to take us to well look at that a carboxylic acid all right a carboxylic acid version of this now you don't have to be great at naming all right as long as you remember what does a carboxylic acid name usually end with noic acid right so which one of these names has noic acid at the end d all right and there you go that's how you answer this question or oic acid i'm so sorry okay fantastic you had a primary alcohol and a strong oxidizing agent you're going to get a carboxylic acid all right and then you know that the ending of any carboxylic acid name is going to be oic acid so that is what you're looking for in the name options all right fantastic i hope this was helpful if you have any questions at all let me know email me comments anything of the sorts if there are any specific problems you want to see send them my way i will do them for you i will work them i will work through them for you all right just you know take that first step of sending it my way or else i wouldn't know okay awesome with that being said good luck happy studying and have a beautiful day future doctors