What are Ketones?

Ketones are compounds in which a carbonyl group is attached to two hydrocarbon groups. According to the different hydrocarbon groups in the molecule, ketones can be divided into fatty ketones, alicyclic ketones, aromatic ketones, saturated ketones and unsaturated ketones. The carbonyl group of an aromatic ketone is directly connected to the aromatic ring; the carbonyl group embedded in the ring is called a cycloendone, such as cyclohexanone. According to the number of carbonyl groups can be divided into monoketones, diketones and polyketones. In a monoketone, the two hydrocarbon groups linked by a carbonyl group are the same as a monoketone, such as acetone (dimethyl ketone). Different from each other are mixed ketones, such as acetophenone (phenylmethyl ketone). Ketones cannot form hydrogen bonds between their molecules, and their boiling points are lower than the corresponding alcohols, but carbonyl oxygen can form hydrogen bonds with water molecules, so ketones (lower ketones) are soluble in water. Lower ketones are liquids with a pleasant odor, and high-carbon ketones (higher ketones) are solids.

Ketones are compounds in which a carbonyl group is attached to two hydrocarbon groups. According to the different hydrocarbon groups in the molecule, ketones can be divided into fatty ketones, alicyclic ketones, aromatic ketones, saturated ketones and unsaturated ketones. The carbonyl group of an aromatic ketone is directly connected to the aromatic ring; the carbonyl group embedded in the ring is called a cycloendone, such as cyclohexanone. According to the number of carbonyl groups can be divided into monoketones, diketones and polyketones. In a monoketone, the two hydrocarbon groups linked by a carbonyl group are the same as a monoketone, such as acetone (dimethyl ketone). Different from each other are mixed ketones, such as acetophenone (phenylmethyl ketone). Ketones cannot form hydrogen bonds between their molecules, and their boiling points are lower than the corresponding alcohols, but carbonyl oxygen can form hydrogen bonds with water molecules, so ketones (lower ketones) are soluble in water. Lower ketones are liquids with a pleasant odor, and high-carbon ketones (higher ketones) are solids.

Chinese name

ketone

Form

A compound in which a carbonyl group is attached to two hydrocarbon groups.

Field

Chemistry

Classification

Fatty Ketones, Alicyclic Ketones, Aromatic Ketones

Functional group

Carbonyl C = O

Response

Reduction reaction addition reaction

Ketone definition

Chemically active, easy to undergo nucleophilic addition reaction with hydrocyanic acid, Grignard reagent, hydroxylamine, alcohol, etc .; can be reduced to alcohol. Under the polarizing action of carbonyl group, ketones with -H can undergo halogenation reaction; under basic conditions, ketones with methyl group can undergo halogenation reaction. It is prepared by oxidation of secondary alcohols, acylation of aromatic hydrocarbons and reaction of carboxylic acid derivatives with organometallic compounds. Acetone and cyclohexanone are important chemical raw materials.

Functional group carbonyl C = O

General formula of ketone: RCOR '

Ketone structure nomenclature

Ketone structure

Ketones all contain carbonyl groups, and their carbonyl carbon atoms

Ketone structure

There are two hydrocarbon groups attached, as shown in the figure on the right.

Ketone nomenclature

Ketones can be divided into two types, aliphatic and aromatic, with the following principles:

Ketone structure

a. Select the longest carbon chain containing a carbonyl group as the main chain;

b Combine the names of the same substituents, indicate the position, and write before the parent ketone name.

Ketone physical properties

Ketone boiling point (degrees Celsius)

Acetone: 56.2

Ketone boiling point (2 photos)

Butanone: 79.6

2-pentanone: 102.4

Ketone solubility

Phenylacetone: 216.5

Solubility of ketones (see right)

Ketone Chemical Properties

If the -C link at C = O has three different volumes,

ketone

Groups, it will cause different steric hindrances on both sides of the carbonyl plane, creating spatial selectivity for nucleophiles to attack carbonyl groups. Groups.

Ketone addition reaction

Nucleophilic addition reaction

The nucleophilic addition of , -unsaturated aldehyde (ketone) is also divided into two cases, 1,2- addition

Unsaturated ketone reaction

And 1,4- additions. The 1,4-addition of , -unsaturated aldehydes (ketones) is actually equivalent to the 3,4- addition.

Michael bonus

A carbanion formed by an active methylene compound and a nucleophilic addition to the carbon-carbon double bond of an , -unsaturated carbonyl compound is an important method for the alkylation of an active methylene compound. Michael reacts. The most important application of Michael's addition is Robinson's ringing reaction. If a cyclic ketone is used as the Michael reaction donor and interacts with methyl vinyl ketone (acceptor), the product 1,5-diketone can be obtained, which can be dehydrated by aldol condensation and dehydration in the molecule. Adding a new six-membered ring, this process is called Robinson ring increase reaction.

Robinson loop

From the viewpoint of modern organic synthesis, the Robinson ring formation reaction actually belongs to a tandem reaction. It is a reaction in which a Michael addition and an aldol condensation phase are connected in series. At the beginning of the reaction, the enolate formed by a carbonyl compound nucleophilically attacked an , -unsaturated ketone, and a Michael addition occurred. The product then undergoes intramolecular aldol condensation to obtain the Robinson ring-forming reaction product.

Nucleophilic addition to HCN

HCN nucleophilic addition

Nucleophilic addition with oxygen sulfur

1. Reaction with H ₂ O-diol

2. Reaction with ROH-formation of acetals (ketones)

Features:

a. The structure of acetal (ketone) is characterized by containing OCO bonds;

b. Acetal (ketone) reaction can be used to protect carbonyl groups;

c. The acetal (ketone) reaction only occurs in the carbonyl group of the aldehyde (ketone), and does not occur for other carbonyl compounds

ketone

This reaction

d. When the molecule contains both a hydroxyl group and an aldehyde (ketone) carbonyl group, an intramolecular acetal (ketone) may occur, forming a five- or six-membered ring;

e. Nucleophilic addition with RSH

f. Nucleophilic addition with NaHSO ₃

The molecule contains both a strong basic group -ONa and a strong acid group -SO ₃ H. The intra-molecular acid-base neutralization makes the reaction irreversible, and the -hydroxysulphonic acid crystals are precipitated from the organic phase, and the -hydroxyl group is formed. Sodium sulfonate can be hydrolyzed to the original aldehyde (ketone) under acidic conditions. Therefore, this reaction can be used for the separation of aldehydes (ketones). -SO ₃ H is a good leaving group,

ketone

Replace with another group by nucleophilic substitution reaction.

Although this method of preparing 2-hydroxypropionitrile goes through two steps, it avoids the dangers caused by the direct use of HCN under acidic conditions.

Addition of ketone to nitrogen-containing nucleophile

The nitrogen-containing nucleophile (G-NH ₂ ) adds aldehydes and ketones to the nucleophile and then eliminates H ₂ O, thereby generating the C = N bond of C = NG:

Imine compounds generated by different G have their own names

Nucleophilic addition with NH ₃

2. Nucleophilic addition to RNH ₂ and ArNH ₂

3. Nucleophilic addition to hydrazine derivatives

4. Nucleophilic addition with H ₂ NOH and Beckmann rearrangement

5. Nucleophilic addition with R ₂ NH to form enamines

Ketone reduction reaction

Catalytic hydrogenation

2. Reductant method

3. Wolff-Kishner-Huang Minglong reduction

4. Carnnizzarro reaction

5. Benzoin condensation

Ketone oxidation reaction

1. Oxidation of Tollens reagent, Fehling reagent and Benedit reagent

2. Baeyer-Villiger oxidation-RCOOOH oxidation

Ketone other

Perkin reaction

Knoevenagel reaction

Wittig reaction

Mannich reaction