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Chapter 16: Problem 38

Draw a structural formula for the product of each acid-catalyzed reaction. (a) Phenylacetaldehyde \(+\) hydrazine \(\longrightarrow\) (b) Cyclopentanone + semicarbazide \(\longrightarrow\) (c) Acetophenone \(+2,4\)-dinitrophenylhydrazine \(\longrightarrow\) (d) Benzaldehyde \(+\) hydroxylamine \(\longrightarrow\)

Short Answer

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Question: Draw the structural formulas for the products of acid-catalyzed reactions involving the following compounds: a) Phenylacetaldehyde + hydrazine b) Cyclopentanone + semicarbazide c) Acetophenone + 2,4-dinitrophenylhydrazine d) Benzaldehyde + hydroxylamine Answer: a) Phenylacetaldehyde hydrazone: C6H5CH2CH=NNH2 b) Cyclopentanone semicarbazone: C5H9N3O c) 2,4-Dinitrophenylhydrazone of acetophenone: C8H8N4O4 d) Benzaldehyde oxime: C6H5CH=NOH

Step by step solution

01

Understand the Reaction Mechanism

In all four reactions, we deal with the reaction of a carbonyl compound (either an aldehyde or a ketone) with a compound carrying an N-H group. The acid-catalyzed mechanism proceeds through the formation of an imine or hydrazone, which is a condensation reaction. The resulting product will have a double bond between the nitrogen and the carbonyl carbon, and the carbonyl oxygen is replaced by the nitrogen-containing group from the second reactant.
02

Reaction (a) Phenylacetaldehyde + hydrazine

For part (a) of the given exercise, we need to draw the product of the reaction between phenylacetaldehyde and hydrazine (N2H4). During the reaction, the carbonyl oxygen of phenylacetaldehyde will be replaced by one of the nitrogen atoms in hydrazine. Product (a): Phenylacetaldehyde hydrazone \[\ce{C6H5CH2CHO + N2H4 -> C6H5CH2CH=NNH2}\]
03

Reaction (b) Cyclopentanone + semicarbazide

For part (b), the reactants are cyclopentanone and semicarbazide. The carbonyl oxygen of cyclopentanone will be replaced by the nitrogen atom of semicarbazide. Product (b): Cyclopentanone semicarbazone \[\ce{C5H8O + H2NNHCONH2 -> C5H9N3O}\]
04

Reaction (c) Acetophenone + 2,4-dinitrophenylhydrazine

In part (c), acetophenone and 2,4-dinitrophenylhydrazine are the reactants. Upon reaction, the carbonyl oxygen of acetophenone will be replaced by the nitrogen atom of 2,4-dinitrophenylhydrazine. Product (c): 2,4-Dinitrophenylhydrazone of acetophenone \[\ce{CH3COC6H5 + H2NNHC6H3(NO2)_2 -> C8H8N4O4}\]
05

Reaction (d) Benzaldehyde + hydroxylamine

Finally, in part (d), benzaldehyde reacts with hydroxylamine. The carbonyl oxygen of benzaldehyde is replaced by the nitrogen atom of hydroxylamine. Product (d): Benzaldehyde oxime \[\ce{C6H5CHO + H2NOH -> C6H5CH=NOH}\] Now that we have found the products for all four reactions, we have completed the task of drawing the structural formulas for the products of each acid-catalyzed reaction.

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Most popular questions from this chapter

Using your roadmaps as a guide, show how to convert acetaldehyde into racemic 3-hydroxybutanal. You must use acetaldehyde as the source of all carbon atoms in the target molecule. Show all reagents and all molecules synthesized along the way.

All rearrangements we have discussed so far have involved generation of an electrondeficient carbon followed by a 1,2 -shift of an atom or group of atoms from an adjacent atom to the electron-deficient carbon. Rearrangements by a 1 ,2-shift can also occur following the generation of an electron-deficient oxygen. Propose a mechanism for the acid-catalyzed rearrangement of cumene hydroperoxide to phenol and acetone.

In Section \(11.5\) we saw that ethers, such as diethyl ether and tetrahydrofuran, are quite resistant to the action of dilute acids and require hot concentrated HI or HBr for cleavage. However, acetals in which two ether groups are linked to the same carbon undergo hydrolysis readily, even in dilute aqueous acid. How do you account for this marked difference in chemical reactivity toward dilute aqueous acid between ethers and acetals?

The base-promoted rearrangement of an \(\alpha\)-haloketone to a carboxylic acid, known as the Favorskii rearrangement, is illustrated by the conversion of 2 -chlorocyclohexanone to cyclopentanecarboxylic acid. (a) Propose a mechanism for base-promoted conversion of 2 -chlorocyclohexanone to the proposed intermediate. (b) Propose a mechanism for base-promoted conversion of the proposed intermediate to sodium cyclopentanecarboxylate.

Both 1,2 -diols and 1,3 -diols can be protected by treatment with 2-methoxypropene according to the following reaction. (a) Propose a mechanism for the formation of this protected diol. (b) Suggest an experimental procedure by which this protecting group can be removed to regenerate the unprotected diol.
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