Ch. 6: Aldehydes and Ketones I

Question 1

Aldehydes

Answer 1

Terminal functional groups containing a carbonyl bonded to at least one hydrogen.

Question 2

Aldehyde nomenclature

Answer 2

Use suffix -al and the prefix oxo-. In rings, they are indicated by the suffix -carbaldehyde

Question 3

Ketones

Answer 3

Internal functional groups containing a carbonyl bonded to two alkyl chains.

Question 4

Ketone nomenclature

Answer 4

Use suffix -ne and the prefix oxo- or keto-

Question 5

Reactivity of carbonyl

Answer 5

C=O; dictated by the polarity of the double bond. The carbon has a partial positive charge and is therefore electrophilic

Question 6

Carbonyl containing compounds vs alcohol properties

Answer 6

Carbonyl containing compounds have higher boiling points than equivalent alkanes bc of dipole interactions. Alcohols have higher boiling points than carbonyls bc of hydrogen bonding

Question 7

How are aldehydes and ketones commonly produced

Answer 7

Oxidation of primary and secondary alcohols, respectively. Weaker, anhydrous oxidizing agents like pyridinium chlorochromate (PCC) must be used for synthesizing aldehydes, or the reaction will continue oxidizing to the level of the carboxylic acid. Various oxidizing agents can be used for ketones, such as dichromate, chromium trioxide, of PCC bc ketones are the most oxidized functional group for secondary carbons

Question 8

When a nucleophile attacks and forms a bond with a carbonyl carbon, electrons in the pi bond are pushed to the oxygen atom

Answer 8

No good leaving group: aldehydes and ketones, the carbonyl will remain open and is protonated to form an alcohol
Good leaving group: carboxylic acids and derivatives, the carbonyl will reform and kick off the leaving group

Question 9

Hydration

Answer 9

In hydration reactions, water adds to a carbonyl forming a geminal diol

Question 10

Hemiacetal/hemiketal

Answer 10

When one equivalent of alcohol reacts w an aldehyde (via nucleophilic addition) a hemiacetal is formed. When the same reaction occurs with a ketone, a hemiketal is formed

Question 11

Acetal/Ketal

Answer 11

when another equivalent of alcohol reacts w a hemiacetal (via nucleophilic substitution) an acetal is formed. When the same reaction occurs with a hemiketal and a ketone, a ketal is formed

Question 12

Imines

Answer 12

Nitrogen and nitrogen derivatives react w carbonyls to form imines, oximes, hydrazones, and semicarbazones

Question 13

Enamines

Answer 13

Imines can tautomerize to form enamines

Question 14

Cyanohydrins

Answer 14

Hydrogen cyanide reacts w carbonyls to form cyanohydrins

Question 15

Hydride reagents

Answer 15

Aldehydes can be oxidized to carboxylic acids using an oxidizing agent like KMnO4, CrO3, Ag2O or H2O2. They can be reduced to primary alcohols va hydride reagents (LiAlH4, NaBH4)

Question 16

Ketone oxidation

Answer 16

Ketones cannot be further oxidized, but can be reduced to secondary alcohols using the same hydride reagents (LiAlH4, NaBH4)