ID: A 79. Give an example of a ketone that would react with a nucleophile at a h
ID: 1083702 • Letter: I
Question
ID: A 79. Give an example of a ketone that would react with a nucleophile at a higher rate than why it would be more reactive acetone, and explain Acetone: 80. Reductions using LiAIH, require a separate acid workup step, while reductions using NaBH, do sot. Explain why to use different polar aprotic solvents to carry out the reaction below. Stadent A chooses tetrahydrofuran. Which is the better choice, and why? 81. Two students decide acetonitrile, while student B chooses 1LiAIH4 82. From the two routes shown below, choose the one that would be best for carrying out the reduction. Explain your choice .NaBH I. Nal 2. H,O 83. Give one example of a hypothetical Grignard reagent that contains an incompatible functional group. 84. The Hormer-Wadsworth-Emmons reaction is a modification of the Wittig reaction that utilizes a phosphonate-stabilized carbanion to produce an alkene. Propose a detailed mechanism for the Horner-Wadsworth-Emmons reaction shown below 1.NaH 2. 47Explanation / Answer
Organic chemistry
79. Acetone with two alkyl (CH3) groups are electron donating and thus any ketone with less electron donating groups would make the carbonyl carbon more electrophilic and would react faster with a nucleophile than acetone. Therefore, 3-oxobutanenitrile (CH3COCH2CN) with a -CN group would react faster than acetone. -CN group pulls electron from carbonyl carbon and makes it more reactive towards nucleophile. Another example would be oxopropanedinitrile (CNCOCN) with two -CN groups directly attached to the C=O functionality is even more reactive.
80. Reduction with strong reducing agents such as LiAlH4 require additional workup step to decompose or neutralize the reagent an acid, whereas, NaBH4 (a weak reducing agent) reduction does not require this acidic workup step as the reagent decomposes itself in the reaction medium (in methanol solvent) overtime.
81. LiAlH4 is a strong reducing agent which can reduce a nitrile group to a primary amine. Therefore, acetonitrile with a -CN functionality is not a good choice for this reduction reaction. Instread tetrhydrofuran is the best choice for this reaction as it is non-reactive with LiAlH4 under the given reaction conditions.
82. NaH is a base, which picks up the alpha hydrogen from the ketone to generate enolate, therefore, using NaH is a bad choice for this reaction. NaBH4 is chemoselctive reagent to reduce aldehyde and ketone and thus is a good choice for doing this reaction.
83. Grignard reagent are basic in nature so any group which has an acidic proton would be incompatible such as HOCH2CH2MgBr, an -OH group is incompatible.