Log out Go to App
Go to App

Learning Materials

Features

Discover

Chapter 16: Problem 25

The Wittig reaction can be used for the synthesis of conjugated dienes, as for example, 1-phenyl-1,3-pentadiene.

Short Answer

Expert verified
Question: Explain the synthesis of 1-phenyl-1,3-pentadiene using the Wittig reaction. Answer: The synthesis of 1-phenyl-1,3-pentadiene using the Wittig reaction involves the reaction of benzaldehyde with 3-pentenyltriphenylphosphonium ylide. The carbanion in the ylide attacks the carbonyl carbon in benzaldehyde, forming a four-membered ring oxaphosphetane intermediate. This intermediate undergoes a concerted decomposition to form the desired product, 1-phenyl-1,3-pentadiene, and triphenylphosphine oxide as a byproduct.

Step by step solution

01

Understanding the Wittig Reaction

The Wittig reaction involves the reaction of an aldehyde or ketone with a phosphonium ylide, which is also known as a Wittig reagent. The product of this reaction is an alkene. The general reaction is as follows: R_1-CHO + R_2_2P=CR_3 ---> R_1-CH=CR_3 + R_2_2PO
02

Identifying the reactants for the synthesis of 1-phenyl-1,3-pentadiene

In order to synthesize 1-phenyl-1,3-pentadiene, we need to identify the appropriate reactants, an aldehyde or ketone and a Wittig reagent. For our desired product: Aldehyde: Benzaldehyde (Ph-CHO) Wittig reagent: 3-pentenyltriphenylphosphonium ylide ((CH_3)_2-CH-PPh_3) Here, Ph stands for the phenyl group (C_6H_5).
03

Reaction of benzaldehyde with Wittig reagent

The benzaldehyde reacts with the Wittig reagent, 3-pentenyltriphenylphosphonium ylide, through a nucleophilic addition process. The carbanion in the ylide attacks the carbonyl carbon in the benzaldehyde molecule, forming a four-membered ring intermediate with a negatively charged oxygen known as an oxaphosphetane. Ph-CHO + (CH_3)_2-CH-PPh_3 -------> Ph-CH(-O^-)-(CH_3)_2-CH-PPh_3^+
04

Formation of the product and byproduct

The oxaphosphetane intermediate undergoes a concerted decomposition, involving a [2+2]-cycloreversion, to form the desired alkene and triphenylphosphine oxide as a byproduct. Ph-CH(-O^-)-(CH_3)_2-CH-PPh_3^+ ------> Ph-CH=CH(CH_3)_2 + Ph_3P=O
05

Identifying the final product

The resulting alkene is the desired product, 1-phenyl-1,3-pentadiene, with the structure: Ph-CH=CH(CH_3)_2 In summary, the Wittig reaction allows the formation of 1-phenyl-1,3-pentadiene by reacting benzaldehyde with 3-pentenyltriphenylphosphonium ylide, followed by the decomposition of the oxaphosphetane intermediate to yield the desired product and triphenylphosphine oxide as a byproduct.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Start your free trial

Over 30 million students worldwide already upgrade their learning with Vaia!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

Following is the final step in the synthesis of the antiviral drug Rimantidine (Problem 7.19). (a) Describe experimental conditions to bring about this conversion. (b) Is Rimantidine chiral? How many stereoisomers are possible for it?

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.

When cis-2-decalone is dissolved in ether containing a trace of \(\mathrm{HCl}\), an equilibrium is established with trans-2-decalone. The latter ketone predominates in the equilibrium mixture.

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.

Starting with cyclohexanone, show how to prepare these compounds. In addition to the given starting material, use any other organic or inorganic reagents as necessary. (a) Cyclohexanol (b) Cyclohexene (c) cis-1,2-Cyclohexanediol (d) 1-Methylcyclohexanol (e) 1-Methylcyclohexene (f) 1-Phenylcyclohexanol (g) 1-Phenylcyclohexene (h) Cyclohexene oxide (i) trans-1,2-Cyclohexanediol
See all solutions

Recommended explanations on Chemistry Textbooks

Nuclear Chemistry

Read Explanation

Kinetics

Read Explanation

Organic Chemistry

Read Explanation

Making Measurements

Read Explanation

Ionic and Molecular Compounds

Read Explanation

Chemical Analysis

Read Explanation
View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free