Propose structures for molecules that fit the following descri...

Question

Propose structures for molecules that fit the following descriptions:

(b) An ester with the formula C₆H₁₂O₂

Accepted Answer

All right. Hi, everyone. So this question is asking us which of the following structures is an ester with a formula of C seven H 1402. Here we have four different answer choices, but it appears that one of them has actually been copied twice. So we can go ahead and actually disregard the last line given and focus on the four compounds labeled A through D. Now recall that an ester is a compound or a functional group with a general formula of R coo R, we have one R group, whether it be A or arrow attached to one carbon. Now, one carbon or the one carbon has a double bond to one oxygen atom as well as a single bond to another. And so the oxygen atom that has a single bond to carbon is attached to another R group can be either A or A. So the molecular formula we're looking for is C seven H 1402. So our first step is going to be to check all four answer choices and make sure they have the correct molecular formula first starting off with option A here which is CH three C two coch two coch two ch three. So starting off with the molecular formula, I can first count how many carbon atoms I see in the structure given of which I counted seven. So that is C seven. And now my next step is to add together all hydrogens connected to all atoms. It going from left to right gear I count three hydrogens on one carbon two, on another two, on another two and three more. So adding all this together gives me a total of 12 hydrogens and I'm seeing two oxygen atoms. So my formula is C seven H 1202. Now based on this alone, right? This cannot be the correct answer because the molecular formula of option A does not match the one given in the question. So now we can proceed with option B. Now option B is CH three ch 25 coo H. So according to the formula, right, we have five different ch two groups which accounts for five carts. So five carbons and two more on either side gives me seven carbons in total. So now I can add my hydrogen, right? I have three carbon or three hydrogens on the left and two carbons in each of the five or two hydrogens, excuse me in each of the five CH two groups as well as one more on the right side. This gives me 14 in total. And I also have two oxygens. Option CCH 32 Chch two coo ch two ch three. Now, here, once again, I have a total of seven carbon atoms and now I can count all of my hydrogens, right? I have three hydrogens from my two ch three groups, one and two and three more. So it's three multiplied by two, add it to one and two and two and three. So that also gives me a total of 14 hydrogens and two oxygens. And then that leaves me with option D which is CH three ch two coch two C h2o ch two CH three. Now, here I also appear to have seven carbons and going from left to right, counting all my hydrogens is three from one carbon, two, from another two, from three more and three from one more. So that gives me a total of 14 as well and two oxygens. So three of my answer choices have a molecular formula of C seven H 402. So now we can compare what functional groups are present, still have to cross out the last part, right. So the first that the first thing I want to point out here is that option B has a general formula of coo H on the right side of the structure. Now recall that R coo H is characteristic of a carboxylic acid. And in the case of compound B, right, we have an R group attached to one carbon on the right side and that one carbon has a double bond to one oxygen and a single bond to another oxygen. Now, the oxygen that has a single bond to carbon is connected to a hydrogen instead of another R group. So option B would not be correct because it is a carboxylic acid and not an ester. So now for options C and D, there's a distinction to make between the locations of the oxygens in compound C and D because not. So in the structure given for option C, both oxygens are written next to each other. Whereas in option D, they are not. Now in the general formula of an ester, right, it is abbreviated as R coo oops R coo R, meaning that the two oxygens of the ester functional group are written next to each other. So in the structure of option C, right, the carbon that immediately to the left of the two oxygens has one double bond to one oxygen and one single bond to the other. Now attached to the oxygen that has a single bond is an ethel group or CH two ch three, right? And on the other side of the carbon that has a double bond, we have another carbon chain as well. So option C is in fact an ester which means that it would be our final answer because notice how in the structure of option D, right, one oxygen has a carbon immediately to its left that has no hydrogen attached to it. This indicates that there is a double bond between them, right? And because on either side of our co here are two different R groups. Option D as a key tone, whereas the other oxygen is connected to two carbons or is in between two carbons that each have hydrogens attached to it. Which means that in addition to the ketone functionality, right, the ketone functional group there is also an ether because the carbon in the center of option D towards the right side has a single bond to both carbons on either side of it. So option D is not correct either. So our answer here is option C in the multiple choice and there you have it. So with that being said, thank you so very much for watching and I hope you found this helpful.

Propose structures for molecules that fit the following descriptions:
(b) An ester with the formula C₆H₁₂O₂

Key Concepts

Ester Functional Group

Molecular Formula Interpretation

Structural Isomerism

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