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Exam 19: The Chemistry of Aldehydes and Ketones

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Question 1

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Provide a detailed, arrow-pushing mechanism for the transformation. Show all reactive intermediates. (It is not necessary to show every resonance structure for appropriate intermediates.)

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This reaction is known as the pinacol rearrangement, where a 1,2-diol under acidic conditions will rearrange to give a carbonyl. The mechanism involves: 11edaded_7d2f_eae3_a31a_371a11e32778_TBMC1048_00

Question 2

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Predict the major organic product of the reaction. If you believe no reaction would occur, write NR and explain why.

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This reaction will r...

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Question 3

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Treatment of a mixture of cyclopentanone (A) and acetone cyanohydrin (B) with a catalytic amount of base (NaOH) leads to an equilibration to form a mixture of A, B, cyclopentanone cyanohydrin (C), and acetone (D). Provide an arrow pushing mechanism for the transformation in the forward direction (A + B → C + D) as written.

For each pair of reactions, circle "faster" for the one you believe is faster. a. ​ b.

Which of the reactions would have the largest K_eq?

In each set of reactions, circle the one with the larger equilibrium constant (lies further to the right). a . ​b.

Identify the missing reagent for the reaction.

Predict the major organic product for the reaction in the box provided. If you believe no reaction would occur, write NR.

Provide detailed, arrow-pushing mechanisms for the two-step transformation. Show all reactive intermediates, and all proton transfer steps. (It is not necessary to show every resonance structure for intermediates.)

The conversion of alkyl azides into primary amines through a procedure called the Staudinger reaction is shown. The mechanism of the first part of the reaction is conceptually similar to the Wittig reaction that we've talked about, where an ylide reacts with a carbonyl to yield an oxaphosphetane, which then rearranges to an alkene and triphenylphosphine oxide. Provide an arrow pushing mechanism for the first part of the Staudinger reaction, the reaction of triphenylphosphine (TPP) and an alkyl azide to produce an iminophosphorane and nitrogen gas.

Outline a synthesis for the transformation. Identify the missing reagents.

Identify the missing reagent for the reaction.

Outline a synthesis to achieve this transformation.

Draw the structure of the major organic product for the reaction. If no reaction would occur, write NR. Unless otherwise stated assume there is enough of any reagent to do all the normal reactions. Reaction mechanisms are not necessary.

Deduce the structure of the missing starting material.

Two students working in a laboratory are tasked to synthesize compound B from compound A. The first student thinks that a dehydration reaction, treating A with strong acid and heat, will do the trick. The second student disagrees and says the reaction will not work as intended. a. Explain why the second student is right and predict the more likely product (C) of the reaction. ​ b. If you could start with cyclohexanone, how would you prepare B? You may use any other reagents you want. Show all steps and intermediates, but reaction mechanisms are not necessary.

Predict the major organic product in the box provided. There may be more than one acceptable answer. If you believe no reaction would occur, write NR. Denote stereochemistry where appropriate.

These two alkenes were prepared by Wittig reactions. In the corresponding box show one set of the carbonyl and ylide reaction partners that would make each alkene. There may be more than one correct answer; just show one. Remember the general form for an ylide is Ph₃P=CR₂. ​a. ​ b.

Outline a synthetic route for the transformation:

In the reaction of H₂O at pH 2 with these compounds, the equilibrium would most favor the geminal dihydroxy product or hydrate for which starting material?