A ketone is a compound in which a carbonyl group is bonded to two hydrocarbon groups. Ketones can be classified into aliphatic ketones, alicyclic ketones, aromatic ketones, saturated ketones, and unsaturated ketones depending on the hydrocarbon group in the molecule.
The carbonyl group of the aromatic ketone is directly attached to the aromatic ring, the carbonyl group is embedded in the ring, which is called a cyclohexanone, such as cyclohexanone.
According to the number of carbonyl groups, it can be further divided into monoketone, diketone, and polyketone. In the monoketone, the two hydrocarbon groups to which the carbonyl group is bonded are the same monoketone, such as acetone (dimethyl ketone).
Different from each other is a mixed ketone such as acetophenone (phenyl methyl ketone).
The ketone molecules cannot form hydrogen bonds, and their boiling points are lower than the corresponding alcohols, but the carbonyl oxygen can form hydrogen bonds with water molecules, so the lower ketones (lower ketones) are soluble in water.
Lower ketones are liquids with a pleasant odor and high carbon number ketones (higher ketones) are solids.
Ketone Functional Group
By the polarization of the carbonyl group, the ketone having α-H can undergo a halogenation reaction; under basic conditions, the ketone having a methyl group can undergo a haloform reaction.
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It is prepared by oxidation of a secondary alcohol, acylation of an aromatic hydrocarbon, and reaction of a carboxylic acid derivative with an organometallic compound. Acetone and cyclohexanone are important chemical raw materials.
Functional group carbonyl C=O
The formula of ketone: RCOR’
a ketone contains a carbonyl group in its molecule and its carbonyl carbon atom
There are two hydrocarbyl groups attached, as shown on the right.
Ketones can be divided into aliphatic and aromatic, the principles are as follows:
a selects the longest carbon chain containing a carbonyl group to do the main chain ;
b Combine the same substituent name, indicate the position, and write it before the ketone parent name.
Ketone boiling point (degrees Celsius)
The solubility of ketones (see photo to the right)
If there are three different volumes in the α-C of C=O
The group will cause different space obstructions on both sides of the carbonyl plane, creating a spatial selectivity for the nucleophile to attack the carbonyl group. We use L, M, and S to represent the large, medium, and small volumes on the α-C, respectively. Group.
Nucleophilic Addition Reaction
The nucleophilic addition of α,β-unsaturated aldehydes (ketones) is also divided into two cases, 1,2-addition
And 1,4-addition. The 1,4-addition of an α,β-unsaturated aldehyde (ketone) is actually equivalent to a 3,4-addition.
The carbanion formed by the active methylene compound and the nucleophilic addition of the carbon-carbon double bond of the α,β-unsaturated carbonyl compound is an important method for the alkylation of the active methylene compound. Michael reacted.
The most important application of Michael’s addition is the Robinson annelation reaction.
If cycloketone is used as a donor for the Michael reaction and reacts with methyl vinyl ketone (receptor), the product 1,5-dione can be obtained, which is condensed and dehydrated by intramolecular aldols, which can be on the original ring.
Adding a new six-membered ring is called the Robinson ring-increasing reaction.
Robinson into a Ring
From the point of view of modern organic synthesis, the Robinson ring-forming reaction actually belongs to a series reaction. It is a reaction in which a Michael addition is combined with an aldol condensation.
At the beginning of the reaction, the enol salt formed by a carbonyl compound nucleophilically attacks an α,β-unsaturated ketone, and Michael addition occurs.
The product is then subjected to intramolecular aldol condensation to give a Robinson ring-forming reaction product.
Nucleophilic addition to HCN
Nucleophilic addition with oxygen-containing sulfur
- React with H 2O – form a diol
- React with ROH – form acetals (ketones)
- The structural feature of the acetal (ketone) is that it contains an OCO bond;
- an acetal (ketone) reaction can be used to protect the carbonyl group;
- The acetal (ketone) reaction occurs only in the carbonyl group of the aldehyde (ketone) and does not occur for other carbonyl compounds.
- When a molecule contains both a hydroxyl group and an aldehyde (ketone) carbonyl group, an intramolecular acetal (ketone) may be formed to form a five- or six-membered ring;
- Nuclear addition with RSH
- Nucleophilic addition to NaHSO 3
The molecule contains both a strongly basic group -ONa and a strong acidic group -SO 3 H. Intramolecular acid-base neutralization makes the reaction irreversible, and crystals of sodium α-hydroxy sulfonate are precipitated from the organic phase, α-hydroxyl Sodium sulfonate can be hydrolyzed to the original aldehyde (ketone) under acidic conditions.
Therefore, the reaction can be used for the separation of aldehydes (ketones). -SO 3 H is a good leaving group and can pass
The nucleophilic substitution reaction is exchanged for other groups.
The method for preparing 2-hydroxy propionitrile, although undergoing two steps, avoids the danger of direct use of HCN under acidic conditions.
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Addition with the nitrogen-containing nucleophile
The nucleophilic addition of the nitrogen-containing nucleophile (G-NH 2 ) to the aldehyde ketone eliminates H2O, thereby producing a C=N bond of C=NG:
Imine compounds produced by G have their own names
1 and NH2. 3 of the nucleophilic addition
- with RNH2 2and ArNH2 2of nucleophilic addition
- The hydrazine derivative of nucleophilic addition
- Nucleophilic addition with H 2NOH and Beckmann rearrangement
- Nucleophilic addition with R 2NH to form an enamine
- Catalytic Hydrogenation
- Reductant method
- Wolff-Kishner- Huang Minglong Restore
- Cannizzaro reaction
- Benzoin condensation
- Oxidation of Tollens reagent, Fehling reagent, and Benedict reagent
- Baeyer-Villiger oxidation – RCOOOH oxidation