7/31/2019 Chapter 15 Aldehydes

1/18

Chapter 15

Aldehydes and Ketones

Milbank High School

7/31/2019 Chapter 15 Aldehydes

2/18

7/31/2019 Chapter 15 Aldehydes

3/18

Objectives/Study Questions

4.How do the solubilities of aldehydes and

ketones of four carbons or less compare to the

solubilities of comparable alkanes and alcohols

in water? 5.How are aldehydes and ketones prepared?

6.What typical reactions take place with

aldehydes and ketones?

7.What are some common aldehydes and

ketones and their uses?

7/31/2019 Chapter 15 Aldehydes

4/18

Carbonyl Group

Carbon atom joined to oxygen by a double

bond

Ketones

Aldehydes

7/31/2019 Chapter 15 Aldehydes

5/18

Aldehydes

Comes from alcohol dehydrogenation Obtained by removing of a hydrogen from

an alcohol

7/31/2019 Chapter 15 Aldehydes

6/18

Aldehydes

Both common and IUPAC names

frequently used

Common names from acids from which

aldehydes can be converted

7/31/2019 Chapter 15 Aldehydes

7/18

Aldehydes

IUPAC

Longest chain with aldehyde

Drop e and add -alAldehyde takes precedence over all other

groups so far

Examples

7/31/2019 Chapter 15 Aldehydes

8/18

Ketones

Naming:

Drop e, add -one

Many common names

Simplest is 3 carbonsC. name: acetone

IUPAC: propanone

7/31/2019 Chapter 15 Aldehydes

9/18

Ketones

Carbonyl carbon gets lowest number

See examples

7/31/2019 Chapter 15 Aldehydes

10/18

Common Carbonyl Compounds

Formaldehyde Manufactured from methanol

Used in many polymers

Acetaldehyde Prepared from ethyl alcohol

Formed in the detoxification of alcohol in the liver

Acetone Formed in the human body as a by-product of lipid

metabolism Excreted in the urine

Hormones Steroid hormones

Progesterone/Testosterone

7/31/2019 Chapter 15 Aldehydes

11/18

Physical Properties of Aldehydes

and Ketones Carbon-oxygen double bond is very polar

Affects boiling points

More than ethers (C-O bonds)

Less than alcohols (C-OH bonds)

Odors Low aldehydes very pungent

High aldehydes pleasant odors (perfumes)

Solubility Similar to alcohols and ethers Soluble up to about 4 carbons

Insoluble after that

7/31/2019 Chapter 15 Aldehydes

12/18

Preparation of Aldehydes

Oxidation

Leads to carboxylic acid unless care is taken

1 alcohols

7/31/2019 Chapter 15 Aldehydes

13/18

Preparation of Ketones

Oxidation of a 2 alcohol

Utilizes chromium compounds and sulfuric

acid

7/31/2019 Chapter 15 Aldehydes

14/18

Chemical Properties of Aldehydes

and Ketones

Both under-go combustion reactions

Oxidation

Aldehydes can be oxidized, ketones cant

See Pg 403

Tollens reagent

Benedicts reagent

Fehlings reagent

7/31/2019 Chapter 15 Aldehydes

15/18

Chemical Properties of Aldehydes

and Ketones

Reduction

Variety of agents can reduce aldehydes and

ketones to alcohols

NaBH4 and H2 commonly used

7/31/2019 Chapter 15 Aldehydes

16/18

Chemical Properties of Aldehydes

and Ketones

Hydration

Formaldehyde dissolves readily in water

Acetaldehyde somewhat also

Form hydrates

7/31/2019 Chapter 15 Aldehydes

17/18

Chemical Properties of Aldehydes

and Ketones

Addition of Alcohols to Carbonyl Groups

Hemiacetal

Aldehyde + alcohol

Hemiketal

Ketone + alcohol

Not very stable

Differs from1 mol to 2 mol

7/31/2019 Chapter 15 Aldehydes

18/18

Chemical Properties of Aldehydes

and Ketones

Hemiacetals + HCl = acetal

Hemiketal + HCl = ketal