Below are organic Compounds A and B . Both compounds are solid at room temperatu

Question

Below are organic Compounds A and B. Both compounds are solid at room temperature. Compound B can be obtained by reducing Compound A in the presence of LAH. Please provide responses to the following questions and statements:

What techniques could be used to determine if a reaction occurred? (In other words, what techniques could be used to determine if starting material remains?)

Give three possible methods in which you could purify the product (Compound B). Please give a detailed description of the processes.

Explanation / Answer

The reduction reaction of Benzoic acid (A) with LiAlH4 will give 2-phenylethanol (B).

This can be confirm this process by analytical techniques,

Benzoic acid will show a peak around 1650 cm-1 corresponds to C=O stretching. And ~3000 cm-1 for -OH stretching.

2-Phenylethanol will only show broad peak ~ 3600 cm-1 for -OH stretching. There will not be any C=O absorption. While the reaction in process the C=O absorption will disappears and the OH band will get enlarges which shows the product formation.

In NMR also we'll find different kinds of signals for Reactant & Product. 1H NMR will show >12ppm for acid H. In case of alcohol the OH proton gives signal only < 7 ppm. and product has more number of protons. from these techniques we can easily find the reaction progress.

Purification

And the two molecules (i,e; reactant & product) are having different boiling points ~250oC & ~218oC respectively. so we can purify the product by using a simple Fractional distillation method.

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