Question

We made esters from carboxylic acids and alcohol. (for one of them, acetic acid + isopentyl alcohol + couple drops of sulfuric acid). Could someone please explain those. Thank you

1. Consider if we had prepared high molecular weight esters, what problems would this pose regarding our method of analysis

2. We used sulfuric acid as a catalyst, but carboxylic acids are a reagent in this reaction. Would simply using excess carboxylic acid work as efficiently as sulfuric acid to catalyze the reaction? Why or why not?

3.Describe a procedure (step by step) that you would follow to prepare benzyl acetate for qualitative (olfactory) analysis

4. ) Briefly and simply describe how we sense smell. Does changing the structure of an ester incrementally (ethyl acetate vs propyl acetate) dramatically change its scent? Why or why not?

Answer 1

The answer are writtned as follows point-wise

Ester Preparation: CH3 Estero H3C- + OH CH3 Drops of H2SO4 - H₂C Isopentyl alcohol (Also known as Isoamyl alcohol) HC CH, + H20 OH Acetic acid 3-Methylbutyl acetate (Also known as Isoamyl acetate)

1. Consider if we had prepared high molecular weight esters, what problems would this pose regarding our method of analysis?

     Quantitative isolation of the esters in short-chain acids is lesser problem, if esters are higher molecular weight alcohols than the method of analysis should be changed. The lower molecular weight ester are analyzed by Gas chromatography mass spectrometry (GC-MS), if the molecular weight is very highly, then the ester analyzed by Tandem mass spectrometry (MS-MS). In reaction, the lower molecular weight alcohols are faster in their reaction. The reaction is slower with alcohols of higher molecular weight.

2. We used sulfuric acid as a catalyst, but carboxylic acids are a reagent in this reaction. Would simply using excess carboxylic acid work as efficiently as sulfuric acid to catalyze the reaction? Why or why not?

No, even using excess carboxylic acids in the reaction, the esterification reaction does not work. The sulfuric acid acting as a catalyst in the reaction which is strong acid the pH is below 1. The strong H+ protonating the carboxylic acid so that it creating the strong electrophilic center, the nucleophile can able to attack the electrophilic center. The carboxylic acids pH 2.5 to 3.5 which is weaker acid unable to create the driving force at the esterification reaction. See the esterification reaction mechanism as follows.   

10: Но H CH3 CH OH ioHK CH3 + oH Cho ho che 2 > CH3 w

3) Describe a procedure (step by step) that you would follow to prepare benzyl acetate for qualitative (olfactory) analysis?

Preparation Benzyl acetate: Ester OH Drops of H2SO4 H3C— 0 CH3 + H20 OH Acetic acid Benzyl alcohol benzyl acetate

Olfactory analysis is the method of analysis that smell starts in the nose with the stimulation of olfactory sensory neurons and terminates in higher cerebral centers which, when activated, make us consciously aware of an odor. Olfactory is the Latin word, which means "to smell”. The nerve's olfactory receptors are located within the mucosa of the nasal cavity. Once the starting material (Acetic acid and Benzyl alcohol) consumed by esterification reaction then the product benzyl acetate is formed. The formed product is ester which has characteristic fruity smell. Then the Olfactory test is completed.

4.) Briefly and simply describe how we sense smell. Does changing the structure of an ester incrementally (ethyl acetate vs propyl acetate) dramatically change its scent? Why or why not?

ma olen samlet HU H3C70 CH3 0 CH3 ethyl acetate propyl acetate

   Once the product (Ester) formation starts at the reaction the sense of the fruity smell is starts. Yes, by changing the structure of the ester in incrementally the smell of intensity of the compound will change dramatically.

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