Structural Elucidation 2

Let's take a look at this question for structure elucidation.
There are 5 observations to consider so let's run this through part by part.
Observation 1
P exhibits optical isomerism, hence a chiral carbon is present in P.
P is neutral so cannot contain acidic functional groups like acid and phenol; and basic functional groups like amine.
P undergoes acid base reaction with sodium so an alcohol functional group is present in P.
Observation 2
P (C5H9ON) undergoes reduction with LiAlH4 to form Q (C5H13ON).
By comparing molecular formula, nitrile functional group is present in P, and primary amine is present in Q.
Cummulative Deduction
So currently we have gathered the following information about P:
- contains chiral C
- has -OH group
- has -CN group on a terminal carbon
Observation 3
Q undergoes oxidation with KMnO4 to form R (C5H11O2N)
By comparing molecular formula, we can deduce a primary alcohol is present in Q and P, and acid group is present in R.
Cummulative Deduction
So now here are the deductions about P:
- contains chiral C
- has primary -OH group on terminal carbon
- has -CN group on a terminal carbon
- has 5 carbons
Since we have quite a few information about P, we can try to figure out the identify of P.
Remember if we can identify a compound as early as possible, it's much easier to figure out the rest of the observations.
Deduce Chain Isomers
For 5 carbon we have 3 possible chain isomers: pentane, 2-methylbutane, 2,2-dimethylpropane
Add Functional Groups and Identify Chiral Carbon
Notice when primary alcohol and nitrile groups are added to each chain isomer, only 2-methylbutane chain isomer will give us a chiral carbon.
Therefore we have 2 possible structures for P identified.
Once P is identified, we can figure out Q and R:
Observation 4
Moving on, R undergoes nucleophilic substitution with SOCl2 to form acid chloride S.
So we can identify S since R is already known.
Observation 5
There is an acid chloride and amine group in S, which can react with each other via condensation to form a neutral cyclic amide in T.
So we can identify both cyclic amides T.
For the in depth discussion for this exercise, do check this video out!
Topic: Organic Chemistry, A Level Chemistry, Singapore
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[@AnnAnnChua]

This question so hard thx for explaining elucidation 3 ?

[@ashishsaulick7172]

Hello chemistry Guru
Can u please make a video on entropy

[@ChemistryGuru]

Hi Ashish thank you for the suggestion! Sure will plan for a video on entropy soon 😄