Ketones

Ketones are organic substances in the molecules of which the carbonyl group is bound to two hydrocarbon radicals.

General formula of ketones: R ₁ -CO-R ₂ .

Among other carbonyl compounds, the presence in ketones of precisely two carbon atoms directly bonded to the carbonyl group distinguishes them from carboxylic acids and their derivatives, as well as aldehydes .

Etymology

The word ketone comes from the old German word Aketon (acetone). It was invented in 1848 by the German chemist Leopold Gmelin (1788-1853) ^[1] .

Nomenclature

The names of aliphatic and alicyclic ketones are formed by adding the suffix -on or -dion (for diketones) to the name of the parental hydrocarbon. Aromatic diketones with ketone groups in the nucleus are called the abbreviated name of the hydrocarbon, adding the suffix -quinone ^[2] .

Other

Trivial nomenclature . For the simplest ketones, their trivial names are used, for example, acetone (for 2-propanone) and benzophenone (for diphenylketone).

The radical functional nomenclature . The name of ketones is allowed according to the radical functional nomenclature, while the name is made up of radicals with a keto group (in alphabetical order) and the name of the class of compounds (functions) is ketone (for example, methyl ethyl ketone - CH ₃ -CO-CH ₂ -CH ₃ ).

Ketone Discovery History

Acetone was discovered by Robert Boyle in 1661 when heating calcium acetate (acetone comes from lat. Acetum - vinegar ):

{\mathsf {Ca(CH_{3}COO)_{2}{\xrightarrow {t}}{}(CH_{3})_{2}CO+CaCO_{3}}}

{\ displaystyle {\ mathsf {Ca (CH_ {3} COO) _ {2} {\ xrightarrow {t}} {} (CH_ {3}) _ {2} CO + CaCO_ {3}}}}

A similar reaction was described by Andreas Libavius - acetone was formed by heating lead sugar ( lead (II) acetate ). The composition of this substance was established only in 1852 by Alexander William Williamson ^[3] .

Physical Properties

Ketones are volatile liquids or fusible solids, lower representatives are highly soluble in water and miscible with organic solvents, some (acetone) mix with water in any ratio. The impossibility of the formation of intermolecular hydrogen bonds leads to their somewhat greater volatility than for alcohols and carboxylic acids with the same molecular weight (for example, acetone boils at 56.1 ° C, and propanol-2 - at 82.4 ° C).

Synthesis Methods

Aromatic ketones can be obtained by the Friedel-Crafts reaction .
By hydrolysis of ketimines.
Of the tertiary peroxoesters, the Krieg rearrangement .
Acid hydrolysis of vic diols .
Oxidation of secondary alcohols . ^[four]
- Oxidation with DMSO .
  1. Swern reaction .
  2. Kornblum reaction .
  3. The Corey-Kim reaction .
  4. The Paris-Dering reaction .

Cycloketones can be obtained by cyclizing Ruzicki .
Hydration of acetylene homologs ( Kucherov reaction ).
Ketones with good yields are obtained by reacting acid chlorides with lithium dialkyl cuprates and alkyl cadmium compounds:

{\mathsf {R_{2}CuLi+R'COCl\rightarrow RC(O)R'+LiCl+CuR}}

{\ displaystyle {\ mathsf {R_ {2} CuLi + R'COCl \ rightarrow RC (O) R '+ LiCl + CuR}}}

{\mathsf {2RCOCl+Cd(C_{2}H_{5})_{2}\rightarrow 2RC(O)C_{2}H_{5}+CdCl_{2}}}

{\ displaystyle {\ mathsf {2RCOCl + Cd (C_ {2} H_ {5}) _ {2} \ rightarrow 2RC (O) C_ {2} H_ {5} + CdCl_ {2}}}}

According to the reaction of Guben - Gosha

Chemical Properties

Keto-Enol Tautomerism

Keto-enol tautomerization. 1 - keto form; 2 - enol form.

Ketones that have at least one alpha-hydrogen atom undergo keto- enol tautomerization . Tautomerization is catalyzed by both acids and bases . As a rule, the keto form is more stable than the enol form. This equilibrium allows ketones to be obtained by hydration of alkynes . The relative stabilization of the enol form by conjugation is the reason for the rather strong acidity of ketones (p K _a ≈ 20) in comparison with alkanes (p K _a ≈ 50).

Hydrogenation

The addition of hydrogen to ketones occurs in the presence of hydrogenation catalysts ( Ni , Co , Cu , Pt , Pd , etc.). Recently, lithium aluminum hydride has often been used as a hydrogenating agent. At the same time, ketones turn into secondary alcohols :

{\mathsf {R_{2}CO+2H\rightarrow R_{2}CH(OH)}}

{\ displaystyle {\ mathsf {R_ {2} CO + 2H \ rightarrow R_ {2} CH (OH)}}}

When ketones are reduced with hydrogen at the moment of their isolation (using alkali metals or magnesium amalgam ), glycols ( pinacones ) are also formed:

{\mathsf {2R_{2}CO+2H\rightarrow R_{2}C(OH){-}CR_{2}(OH)}}

{\ displaystyle {\ mathsf {2R_ {2} CO + 2H \ rightarrow R_ {2} C (OH) {-} CR_ {2} (OH)}}}

Nucleophilic addition reactions

Reactions with alkyl magnesium halides lead to secondary alcohols.
The reaction with hydrocyanic acid leads to α-hydroxy nitriles, the saponification of which produces α-hydroxy acids:

{\mathsf {(CH_{3})_{2}CO+HCN\rightarrow (CH_{3})_{2}C(OH)CN}}

{\ displaystyle {\ mathsf {(CH_ {3}) _ {2} CO + HCN \ rightarrow (CH_ {3}) _ {2} C (OH) CN}}}

{\mathsf {(CH_{3})_{2}C(OH)CN+2H_{2}O\rightarrow (CH_{3})_{2}C(OH)COOH+NH_{3}}}

{\ displaystyle {\ mathsf {(CH_ {3}) _ {2} C (OH) CN + 2H_ {2} O \ rightarrow (CH_ {3}) _ {2} C (OH) COOH + NH_ {3} }}}

They react with ammonia very slowly:

{\mathsf {(CH_{3})_{2}CO{\xrightarrow[{OH-}]{}}(CH_{3})_{2}C{=}CH{-}C(O){-}CH_{3}{\xrightarrow[{+NH_{3}}]{}}(CH_{3})_{2}C(NH_{2})CH_{2}{-}C(O){-}CH_{3}}}

{\ displaystyle {\ mathsf {(CH_ {3}) _ {2} CO {\ xrightarrow [{OH -}] {}} (CH_ {3}) _ {2} C {=} CH {-} C ( O) {-} CH_ {3} {\ xrightarrow [{+ NH_ {3}}] {}} (CH_ {3}) _ {2} C (NH_ {2}) CH_ {2} {-} C ( O) {-} CH_ {3}}}}

The addition of sodium hydrosulfite gives hydrosulfite (bisulfite) derivatives (only methyl ketones enter the reaction in a fat series):

{\mathsf {RC(O)CH_{3}+HSO_{3}Na\rightarrow R{-}C(OH)(SO_{3}Na){-}CH_{3}}}

{\ displaystyle {\ mathsf {RC (O) CH_ {3} + HSO_ {3} Na \ rightarrow R {-} C (OH) (SO_ {3} Na) {-} CH_ {3}}}}

When heated with a solution of soda or mineral acid, the hydrosulfite derivatives decompose with the release of free ketone:

{\mathsf {2R{-}C(OH)(SO_{3}Na){-}CH_{3}+Na_{2}CO_{3}\rightarrow 2RC(O)CH_{3}+2Na_{2}SO_{3}+CO_{2}+H_{2}O}}

{\ displaystyle {\ mathsf {2R {-} C (OH) (SO_ {3} Na) {-} CH_ {3} + Na_ {2} CO_ {3} \ rightarrow 2RC (O) CH_ {3} + 2Na_ {2} SO_ {3} + CO_ {2} + H_ {2} O}}}

Ketones form ketoximes with hydroxylamine , releasing water:

{\mathsf {(CH_{3})_{2}CO+NH_{2}OH\rightarrow H_{2}O+(CH_{3})_{2}C{=}N{-}OH}}

{\ displaystyle {\ mathsf {(CH_ {3}) _ {2} CO + NH_ {2} OH \ rightarrow H_ {2} O + (CH_ {3}) _ {2} C {=} N {-} OH }}}

Depending on the conditions, hydrazones are formed with hydrazine (the ratio of hydrazine to ketone is 1: 1) or azines (1: 2):

{\mathsf {(CH_{3})_{2}CO+N_{2}H_{4}\rightarrow (CH_{3})_{2}C{=}N{-}NH_{2}+H_{2}O}}

{\ displaystyle {\ mathsf {(CH_ {3}) _ {2} CO + N_ {2} H_ {4} \ rightarrow (CH_ {3}) _ {2} C {=} N {-} NH_ {2 } + H_ {2} O}}}

{\mathsf {2(CH_{3})_{2}CO+N_{2}H_{4}\rightarrow (CH_{3})_{2}-C{=}N{-}N{=}C-(CH_{3})_{2}+2H_{2}O}}

{\ displaystyle {\ mathsf {2 (CH_ {3}) _ {2} CO + N_ {2} H_ {4} \ rightarrow (CH_ {3}) _ {2} -C {=} N {-} N {=} C- (CH_ {3}) _ {2} + 2H_ {2} O}}}

As in the case of aldehydes, when heated with solid KOH, ketone hydrazone emit nitrogen and give saturated hydrocarbons ( Kizhner reaction )

Acetals of ketones are more complex than acetals of aldehydes - the action of orthoform HC (OC ₂ H ₅ ) ₃ or orthosilicic acid on ketones.

Condensation Reactions

Under harsh conditions (in the presence of alkalis), ketones undergo aldol condensation . In this case, β-keto alcohols are formed, which easily lose a water molecule.

Under even more severe conditions, for example, when heated with concentrated sulfuric acid , ketones undergo intermolecular dehydration with the formation of unsaturated ketones:

{\mathsf {2(CH_{3})_{2}CO\rightarrow H_{2}O+(CH_{3})_{2}C{=}CH{-}C(O){-}CH_{3}}}

{\ displaystyle {\ mathsf {2 (CH_ {3}) _ {2} CO \ rightarrow H_ {2} O + (CH_ {3}) _ {2} C {=} CH {-} C (O) {- } CH_ {3}}}}

Mesityl oxide can react with a new acetone molecule to form phoron :

{\mathsf {(CH_{3})_{2}C{=}CH{-}C(O){-}CH_{3}+(CH_{3})_{2}CO\rightarrow (CH_{3})_{2}C{=}CH{-}C(O){-}CH{=}C(CH_{3})_{2}}}

{\ displaystyle {\ mathsf {(CH_ {3}) _ {2} C {=} CH {-} C (O) {-} CH_ {3} + (CH_ {3}) _ {2} CO \ rightarrow (CH_ {3}) _ {2} C {=} CH {-} C (O) {-} CH {=} C (CH_ {3}) _ {2}}}}

The recovery of ketones, the Leykart-Wallach reaction, can be attributed to a separate type of reaction.

Essential Ketones

Title	Formula	Melting temperature	Boiling temperature
Acetone (dimethyl ketone)	CH ₃ —CO — CH ₃	−95 ° C	56.1 ° C
Methyl ethyl ketone	CH ₃ CH ₂ -CO-CH ₃	−86 ° C	80 ° C
Diethyl ketone	CH ₃ CH ₂ COCH ₂ CH ₃	−40 ° C	102 ° C
Acetophenone		19 ° C	202 ° C
Benzophenone		47.9 ° C	305.4 ° C
Cyclohexanone		−16.4 ° C	155.65 ° C
Diacetyl	CH ₃ COCOCH ₃	−3 ° C	88 ° C
Acetylacetone	CH ₃ COCH ₂ COCH ₃	−23 ° C	140 ° C
Parabenzoquinone		115 ° C	-

Biochemistry

Toxic. They have an irritating and local effect, penetrate the skin, especially well-unsaturated aliphatic. Certain substances have a carcinogenic and mutagenic effect. Halogenated ketones cause severe irritation of the mucous membranes and burns in contact with skin. Alicyclic ketones have a narcotic effect.

Ketones play an important role in the metabolism of substances in living organisms. So, ubiquinone is involved in redox reactions of tissue respiration. Compounds containing a ketone group include some important monosaccharides ( fructose , etc.), terpenes ( menton , carvone ), components of essential oils ( camphor , jasmone ), natural dyes ( indigo , alizarin , flavones ), steroid hormones ( cortisone , progesterone ), musk ( muskon ), the antibiotic tetracycline .

In the process of photosynthesis of 1,5-diphosphate-D-erythro-pentulose (phosphated ketopentose) is a catalyst. Acetoacetic acid is an intermediate in the Krebs cycle.

The presence of ketones in the urine and blood of a person indicates hyperglycemia, various metabolic disorders or ketoacidosis .

Application

In industry, ketones are used as solvents, pharmaceuticals and for the manufacture of various polymers. The most important ketones are acetone, methylethyl ketone and cyclohexanone ^[5] .

Notes

↑ http://www.etymonline.com/index.php?term=ketone Online Etymology Dictionary
↑ IUPAC Nomenclature of Organic Chemistry . ACD / Labs. Date of treatment August 24, 2009. Archived August 21, 2011.
↑ Aksyonova M., Leenson I. Chemistry. Encyclopedia for children. - Avanta +, 2007 .-- P. 357-359. - ISBN 978-5-98986-036-4 .
↑ Receive. (unspecified) . medlec.org. Date of treatment July 20, 2016.
↑ Hardo Siegel, Manfred Eggersdorfer. “Ketones” // Ullmann's Encyclopedia of Industrial Chemistry. - 2005. - DOI : 10.1002 / 14356007.a15_077 .

Literature

General toxicology / ed. A.O. Loit. SPb .: ELBI-SPb., 2006
Chemical Encyclopedia in 5 volumes ed. I. L. Knunyants 2 volume

[1] ttp://www.etymonline.com/index.php?term=ketone Online Etymology Dictionary

[2] IUPAC Nomenclature of Organic Chemistry . ACD / Labs. Date of treatment August 24, 2009. Archived August 21, 2011.

[3] Aksyonova M., Leenson I. Chemistry. Encyclopedia for children. - Avanta +, 2007 .-- P. 357-359. - ISBN 978-5-98986-036-4 .

[4] Receive. (unspecified) . medlec.org. Date of treatment July 20, 2016.

[5] Hardo Siegel, Manfred Eggersdorfer. “Ketones” // Ullmann's Encyclopedia of Industrial Chemistry. - 2005. - DOI : 10.1002 / 14356007.a15_077 .