WWU -- Chemistry Aldehydes and Ketones II. Oxidation and Reduction: Synthesis Chapter 17.
Reduction of Aldehydes and Ketones
description
Transcript of Reduction of Aldehydes and Ketones
![Page 1: Reduction of Aldehydes and Ketones](https://reader033.fdocuments.net/reader033/viewer/2022061317/56814944550346895db68e48/html5/thumbnails/1.jpg)
Reduction of Aldehydes and Ketones
119.8 Reduction of Aldehydes and Ketones to Alcohols
![Page 2: Reduction of Aldehydes and Ketones](https://reader033.fdocuments.net/reader033/viewer/2022061317/56814944550346895db68e48/html5/thumbnails/2.jpg)
Reduction with LiAlH4 and NaBH4
219.8 Reduction of Aldehydes and Ketones to Alcohols
![Page 3: Reduction of Aldehydes and Ketones](https://reader033.fdocuments.net/reader033/viewer/2022061317/56814944550346895db68e48/html5/thumbnails/3.jpg)
Reduction with LiAlH4
• LiAlH4 serves as a source of hydride ion (H:-)
• LiAlH4 is very basic and reacts violently with water; anhydrous solvents are required
319.8 Reduction of Aldehydes and Ketones to Alcohols
![Page 4: Reduction of Aldehydes and Ketones](https://reader033.fdocuments.net/reader033/viewer/2022061317/56814944550346895db68e48/html5/thumbnails/4.jpg)
Reduction with LiAlH4
• Like other strong bases, LiAlH4 is also a good nucleophile
• Additionally, the Li+ ion is a built-in Lewis-acid
419.8 Reduction of Aldehydes and Ketones to Alcohols
![Page 5: Reduction of Aldehydes and Ketones](https://reader033.fdocuments.net/reader033/viewer/2022061317/56814944550346895db68e48/html5/thumbnails/5.jpg)
Reduction with LiAlH4
• Each of the remaining hydrides become activated during the reaction
519.8 Reduction of Aldehydes and Ketones to Alcohols
![Page 6: Reduction of Aldehydes and Ketones](https://reader033.fdocuments.net/reader033/viewer/2022061317/56814944550346895db68e48/html5/thumbnails/6.jpg)
Reduction with NaBH4
• Na+ is a weaker Lewis acid than Li+ requiring the use of protic solvents
• Hydrogen bonding then serves to activate the carbonyl group
619.8 Reduction of Aldehydes and Ketones to Alcohols
![Page 7: Reduction of Aldehydes and Ketones](https://reader033.fdocuments.net/reader033/viewer/2022061317/56814944550346895db68e48/html5/thumbnails/7.jpg)
Reduction with LiAlH4 and NaBH4
• Reactions by these and related reagents are referred to as hydride reductions
• These reactions are further examples of nucleophilic addition
719.8 Reduction of Aldehydes and Ketones to Alcohols
![Page 8: Reduction of Aldehydes and Ketones](https://reader033.fdocuments.net/reader033/viewer/2022061317/56814944550346895db68e48/html5/thumbnails/8.jpg)
Selectivity with LiAlH4 and NaBH4
• LiAlH4 reduces all carbonyl groups
• NaBH4 is less reactive– Reduces
• Aldehydes• Ketones• Esters (slowly)
– Does not reduce• Carboxylic acids• Amides• Nitro groups• Alkyl halides• Alkyl tosylates
819.8 Reduction of Aldehydes and Ketones to Alcohols
![Page 9: Reduction of Aldehydes and Ketones](https://reader033.fdocuments.net/reader033/viewer/2022061317/56814944550346895db68e48/html5/thumbnails/9.jpg)
Problems
• Which reducing agent, LiAlH4 or NaBH4 is more appropriate for reduction of the following reagents? Draw the products.
9
![Page 10: Reduction of Aldehydes and Ketones](https://reader033.fdocuments.net/reader033/viewer/2022061317/56814944550346895db68e48/html5/thumbnails/10.jpg)
Reduction by Catalytic Hydrogenation
• Hydride reagents are more commonly used• However, catalytic hydrogenation is useful for
selective reduction of alkenes
1019.8 Reduction of Aldehydes and Ketones to Alcohols
![Page 11: Reduction of Aldehydes and Ketones](https://reader033.fdocuments.net/reader033/viewer/2022061317/56814944550346895db68e48/html5/thumbnails/11.jpg)
Grignard Addition
• Grignard reagents with carbonyl groups is the most important application of the Grignard reagent in organic chemistry
1119.9 Reactions of Aldehydes and Ketones with Grignard and Related Reagents
![Page 12: Reduction of Aldehydes and Ketones](https://reader033.fdocuments.net/reader033/viewer/2022061317/56814944550346895db68e48/html5/thumbnails/12.jpg)
Grignard Addition
1219.9 Reactions of Aldehydes and Ketones with Grignard and Related Reagents
![Page 13: Reduction of Aldehydes and Ketones](https://reader033.fdocuments.net/reader033/viewer/2022061317/56814944550346895db68e48/html5/thumbnails/13.jpg)
Importance of the Grignard Addition
• This reaction results in C-C bond formation
• The synthetic possibilities are almost endless
1319.9 Reactions of Aldehydes and Ketones with Grignard and Related Reagents
![Page 14: Reduction of Aldehydes and Ketones](https://reader033.fdocuments.net/reader033/viewer/2022061317/56814944550346895db68e48/html5/thumbnails/14.jpg)
Importance of the Grignard Addition
1419.9 Reactions of Aldehydes and Ketones with Grignard and Related Reagents
![Page 15: Reduction of Aldehydes and Ketones](https://reader033.fdocuments.net/reader033/viewer/2022061317/56814944550346895db68e48/html5/thumbnails/15.jpg)
Grignard Addition
• R-MgX reacts as a nucleophile; this group is also strongly basic behaving like a carbanion
• The addition is irreversible due to this basicity
1519.9 Reactions of Aldehydes and Ketones with Grignard and Related Reagents
![Page 16: Reduction of Aldehydes and Ketones](https://reader033.fdocuments.net/reader033/viewer/2022061317/56814944550346895db68e48/html5/thumbnails/16.jpg)
Problems
• Give the products for the following Grignard reactions:
16
![Page 17: Reduction of Aldehydes and Ketones](https://reader033.fdocuments.net/reader033/viewer/2022061317/56814944550346895db68e48/html5/thumbnails/17.jpg)
Organolithium and Acetylide Reagents
• These reagents react with aldehydes and ketones analogous to Grignard reagents
1719.9 Reactions of Aldehydes and Ketones with Grignard and Related Reagents
![Page 18: Reduction of Aldehydes and Ketones](https://reader033.fdocuments.net/reader033/viewer/2022061317/56814944550346895db68e48/html5/thumbnails/18.jpg)
Problems
• Give the products for the following rxns:
18
![Page 19: Reduction of Aldehydes and Ketones](https://reader033.fdocuments.net/reader033/viewer/2022061317/56814944550346895db68e48/html5/thumbnails/19.jpg)
Reactions with Amines
19
Secondary Amine
![Page 20: Reduction of Aldehydes and Ketones](https://reader033.fdocuments.net/reader033/viewer/2022061317/56814944550346895db68e48/html5/thumbnails/20.jpg)
20
Reactions with Primary Amines
![Page 21: Reduction of Aldehydes and Ketones](https://reader033.fdocuments.net/reader033/viewer/2022061317/56814944550346895db68e48/html5/thumbnails/21.jpg)
• Dehydration is typically the rate-limiting step
21
![Page 22: Reduction of Aldehydes and Ketones](https://reader033.fdocuments.net/reader033/viewer/2022061317/56814944550346895db68e48/html5/thumbnails/22.jpg)
Reactions with Secondary Amines
22
![Page 23: Reduction of Aldehydes and Ketones](https://reader033.fdocuments.net/reader033/viewer/2022061317/56814944550346895db68e48/html5/thumbnails/23.jpg)
23
![Page 24: Reduction of Aldehydes and Ketones](https://reader033.fdocuments.net/reader033/viewer/2022061317/56814944550346895db68e48/html5/thumbnails/24.jpg)
Problems
1) Draw the products for the following reactions:
24
![Page 25: Reduction of Aldehydes and Ketones](https://reader033.fdocuments.net/reader033/viewer/2022061317/56814944550346895db68e48/html5/thumbnails/25.jpg)
2) Draw the mechanism for the formation of the imine in the previous question
25