CHE 3332 – Organic Chemistry 2 – Spring 2021 Week 11 Resource

Hello everyone! Virtual group tutoring for this class will be every Tuesday from 6-7 pm, and you can reserve your spot by making an appointment at www.Baylor.edu/Tutoring. This week, we’ll cover Part 2 of Chapter 20: Ketones & Aldehydes and look at naming for Chapter 21: Carboxylic Acid Derivatives. Keywords: Wolff-Kishner, sulfur reactions, cyanohydrin, Wittig, Baeyer-Villiger

Wolff-Kishner Reduction – reduction of hydrazone to alkane This is under basic conditions, with either KOH, KOt, or KOt-Bu as reagents. Reduction removed the double bond and the connected nitrogen groups. Order of 5 step reaction: three proton transfers, leaving group leaves, proton transfer.

Sulfur Nucleophilic Reactions • A ketone with two thiols creates a thioacetal (similar to acetal formation). Desulfurization can then occur, which is reduction of thioacetal to alkane (similar to Wolff-Kishner).

• An aldehyde creates a dithiane – this is similar to a thioacetal except it has an acidic proton. The reagent nBuLi replaces the acidic proton with a negative charge, making the structure reactive. The reagents Hg2+/H2O take off dithiane from the structure and replaces it with a carbonyl.

Hydrogen Nucleophilic Reactions – reduction of ketone to secondary alcohol. There are two sets of reagents that will make the same product. Note that strong reducing agents are needed to reduce the carbonyl.

Cyanohydrin Reactions • A ketone with HCN, NaCN with HCl, or KCN with HCl as reagents can make a cyanohydrin.

• Cyanohydrin with acidic hydronium ion can make a carboxylic acid:

• Cyanohydrin with a strong reducing agent like LAH makes a hydroxyamine. The triple bonded nitrogen gets reduced to a single bonded nitrogen.

Wittig Reaction A ketone or aldehyde reacts with a phosphorous ylide to make an alkene. To create the ylide, a phosphonium salt reacts with BuLi. There are two final products in this reaction: an alkene, which stems from the ketone, and a triphenyl phospheneoxide. There are several steps and intermediates to this reaction. Know the names of all the structures!

Description of steps: reactive ylide attacks carbonyl, betaine forms, betaine reorients into a square formation so the phosphorus and oxygen are adjacent, reactive oxygen attacks the phosphorus, oxaphosphetane forms, 2 single bonds rearrange to break the structures and create 2 products each with its own double bond

Example: predict the product of this Wittig reaction

Baeyer-Villiger Oxidation A ketone or aldehyde reacts with a peracid to make an ester. The original structure rearranges to fit the new oxygen because the oxygen must be adjacent to the carbonyl.

• When the ketone is unsymmetrical, the more substituted group bonds to the oxygen:

Looking ahead to Chapter 21: Carboxylic Acids & Derivatives – naming chart

Derivative How to name the structure Naming example Carboxylic Acid • -remove “e” and add -oic acid • for a ring, keep the “e” and add -carboxylic acid • for diacids, keep the “e” and add -dioic acid Butanoic acid

Acid Halide • replace “ic acid” with -yl halide • for a ring, keep the “e” and add -carbonyl chloride

Benzoyl chloride Ester • replace “ic acid” with -ate • group on oxygen does in front • for a ring, keep the “e” and add -carboxylate

Ethyl acetate

Amide • replace “ic acid” with -amide • for a ring, keep the “e” and add -carboxamide

Acetamide

Anhydride • replace “acid” with anhydride • if unsymmetrical, put acidic compounds in alphabetical order

Acetic benzoic anhydride

Quiz: Name the type of reaction and complete it:

1.

2.

3.

Answers: All questions sourced from the Wiley Organic Chemistry Second Semester textbook.

1. Sulfur Nucleophilic Reaction

2. Cyanohydrin

3. Baeyer-Villiger with unsymmetrical ketone