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 Found this video useful? Please LIKE this video and SHARE it with your friends! Any feedback, comments or questions to clarify? Suggestions for new video lessons? Drop them in the COMMENTS Section, I would love to hear from you! You can also view this video lesson with screenshots and detailed explanation at chemistryguru.com.sg/structural-elucidation-2 Do check out the following for more video lessons: Organic Chemistry Videos at chemistryguru.com.sg/a-level-organic-chemistry-vid… A Level Chemistry Videos at chemistryguru.com.sg/a-level-chemistry-video-lesso… If you are looking for H2 Chemistry Tuition, do consider taking up my classes at Bishan. More info at chemistryguru.com.sg/ Or you can save both time and cost by learning A Level Chemistry online! Find out more at chemistryguru.com.sg/online-tuition-singapore ~-~~-~~~-~~-~ Please watch my latest video: "2019 P1 Q2 - Deflection of Charged Particle in Electric Field"    • 2019 P1 Q2 - Deflection of Charged Pa...   ~-~~-~~~-~~-~

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