protic , aprotic question

[joonkimdds]

The problem says

"In which solvent would u expect benzoic acid to be least acidic?

the choices were
a) CH3CH2OH
b) HOH
c) CH3CH2-O-CH2-CH3
d) CH3CH2NH2

and the answer was
CH3CH2-O-CH2-CH3

the explanation says
"polar aprotic solvents decreases acidity"

I couldn't understand this well so I asked a professor and all she said was
benzoic acid ends with oic so it's carboxylic acid.

what does she mean? what does carboxilic acid have to do with this problem?

I thought that all i need to know is choice c is the only aprotic and other 3 choices are protic and that's all it matters???

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[blue_moon01]

both you and your prof is right.

your reason for choosing C is right....
But your prof just gave you the reason why your choice is right.
Benzoic has a carboxylic functional group which means that if it's in an aprotic solution like Choice C, it's acidity would decrease due to reaction between the O in Choice "C" and the H in the carboxylic group.

I think she just meant for you to understand that the answer lies in knowing the functional group of the substance in question and how it's acidity is affected by the solution.

it looks like you know your stuff !!

 

[joonkimdds]

both you and your prof is right.

your reason for choosing C is right....
But your prof just gave you the reason why your choice is right.
Benzoic has a carboxylic functional group which means that if it's in an aprotic solution like Choice C, it's acidity would decrease due to reaction between the O in Choice "C" and the H in the carboxylic group.

I think she just meant for you to understand that the answer lies in knowing the functional group of the substance in question and how it's acidity is affected by the solution.

it looks like you know your stuff !!

On the other hand, Protic can solvate both + and - while Aprotic can only solvate + but not the -. This makes aprotic to discourage the dissociation of ion and makes - less acidic. (I think...) so in this case, is carboxylic group -?
if it's not + then both protic and aprotic can solvate it and there is not much difference?

 

[Lily-VA]

omg...
I read this question about 3 times. Really time for me to go to bed.
I remember now..my biochem teacher told me (you must know Dr.Bobrik^^ I go to same school with you) that anytime you havae -OH and -NHR.. bonds, they are polar meaning protic. Hope this helps your clarification 🙂