Organic Chemistry 232L Final Exam TA: Zae, Janise, Frank Name: Aboliul Rahmen Dw

Question

Organic Chemistry 232L Final Exam TA: Zae, Janise, Frank Name: Aboliul Rahmen Dwere I) What defines a good and weak nucleophile? 5 points 2) What role does solvent play in SNi and Sz reaction? 5 points 3) Give the definition of a catalyst. 5 points 4) How does the sp hybridization change from ketone to alcohol? 5 points 5) Compare and contrast lithium aluminum hydride and sodium borohydride. Why was NaBH, used instead of LiALH? 5 points 6) Why is the oxidation of organic compound an important category of reactions? 5 points

Explanation / Answer

1) Compounds which are capable of donating a pair of electron easily is a good nuceophile. Whereas donating capacity of weak nucleophile is less. Weak nucleophile are least basic ph<8. Whereas ph ranging from 9 to 14 are strong nucleophile.

2)SN1 reaction is not affected by presence of solvent as intermediate is carbocation. Whereas in SN2 reaction highly polar solvent substitutes with compound which is less polar. Intermediate is carbon with valency 5.

3)Catalyst are the compound which does not take part in chemical reaction but speed up the rate of chemical reaction.

4)In ketone Carbon and oxygen both are sp2 hybridised. When ketone undergoes reduction electron pair from carbonyl atom shifts to oxygen thus forming carbonyl group sp hybridised. Then electron pair from oxygen is accepted by hydrogen forming alcohol.

5) LiAlH4 being stronger reducing agent than NaBH4 then too NaBH4 is preferred. LiAlH4 react with vigorously and violently when released in atmosphere also it may catch fire on room temperature, whereas NaBH4 react slowly and safe for practical use.

6) Many useful chemical drugs acid can be prepared from just oxidation. Oxidation also plays a main role in body fat metabolism. Thus oxidation is important category of reaction.

FOR EG=Alcohol get oxidized to aldehyde and aldehyde further to Carboxylic acid

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