Isovanillin

  • 3-hydroxy -4-methoxybenzaldehyde
  • 3- Hydroxyanisaldehyd

Pale yellow crystal shining pillars

Fixed

113-115 ° C

179 ° C (15 mmHg; ≈ 20 hPa)

8.89 (25 ° C)

Easily in hot water, sparingly soluble in cold; very slightly soluble in chloroform, slightly in ethanol, ether, methanol and glacial acetic acid

Attention

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Isovanillin ( 3-hydroxy -4-methoxybenzaldehyde ) is an organic chemical compound with the molecular formula C8H8O3. It is a derivative of benzaldehyde having an additional hydroxyl and a methoxy group. Isovanillin is an isomer of vanillin, from which it differs only by the position of the methoxy group. It is virtually odorless in contrast. It is a synthesis module, which, in the pharmaceutical, cosmetic, agricultural and food industry mainly used.

  • 3.1 Physical Properties
  • 3.2 Chemical Properties
  • 3.3 Biological Properties

History and habitat

Isovanillin 1882 was isolated and characterized by Rudolf Wegscheider. It depends, inter alia, in front of Mondia whitei and cassava.

Production and representation

Natural sources

The isolation of isovanillin done either by extraction with various solvents but also by steam distillation from the dried roots of Mondia whitei.

Technical syntheses

Numerous processes are known for displaying:

  • Piperonal ( 3,4 - ( methylenedioxy ) benzaldehyde ) is reacted with sodium methoxide in the presence of copper ( I) chloride in dimethylformamide.
  • Veratraldehyde (3,4- Dimethoxybenzaldehyde ) can be implemented by selective demethylation with methionine in methanesulfonic acid to isovanillin. The reaction times are long, and the selectivity is not very high.
  • A selective O-methylation of protocatechualdehyde (3,4- dihydroxybenzaldehyde ) with methyl iodide in the presence of sodium hydride in dimethyl sulfoxide leads to a yield of about 65% of isovanillin.
  • Formylation of guaiacol (o- methoxyphenol ), which is protected as an acetate, is carried out with Dichlormethoxymethan in the presence of titanium tetrachloride in dichloromethane. 3- acetoxy -4-methoxybenzaldehyde is then hydrolyzed with NaOH.
  • Isovanillin can be obtained in good yield by selectively in 3-position of the alkyl group is split off with a 3 -alkoxy -4-methoxybenzaldehyde using a strong acid, wherein the alkoxy group contains at least two carbon atoms. You should create it, inter alia, ethyl vanillin (1 ), which is methylated with dimethyl sulfate to the 3- ethoxy -4-methoxybenzaldehyde (2). Of ethyl ether is then selectively cleaved with sulfuric acid.

Properties

Physical Properties

Isovanillin forms pale yellow crystal shining pillars, melts at 113-115 ° C and boils at 179 ° C under reduced pressure ( 15 mmHg; ≈ 20 hPa). It is easily in hot water, sparingly soluble in cold; however, it is readily soluble in chloroform, ethanol, ether, methanol and glacial acetic acid. It crystallizes in the monoclinic crystal system, space group P21 / a with lattice parameters a = 851.7 pm, b = 1338.0 pm, c = 639.0 pm, β = 97.21 ° and four formula units per unit cell.

Chemical Properties

Isovanillin derived structurally from both the benzaldehyde and from guaiacol (2- methoxyphenol ). It is different than isomer of vanillin by the position of the methoxy group. Rather than at position 3 is this to be found here at position 4. Hydroxy and methoxy exchange places compared to vanillin. In contrast to vanillin, it is virtually odorless.

It forms with an aqueous solution of iron (III ) chloride, but no color. The pKa of the phenolic OH group is 8.89 (25 ° C). This value is compared with the phenol with 9.99 lower; the aldehyde is increased by electron-withdrawing its - M effect of the OH acidity; the phenolic OH bond is increasingly polarized.

Biological Properties

Isovanillin is a selective inhibitor of aldehyde oxidase. It is not a substrate of this enzyme and is metabolized by aldehyde dehydrogenase to Isovanillinsäure.

Structural Related

Isovanillylalkohol (3- hydroxy-4- methoxybenzyl ) formed by reduction of isovanillin. Isovanillinsäure (3- hydroxy-4- methoxybenzoic acid ) is formed by oxidation, for example, enzymatic way.

Isoethylvanillin (3- hydroxy-4- ethoxybenzaldehyde ), a structural relative of and differs from isovanillin by replacing the methyl group to an ethyl group. The structure corresponds to the analogy. Between vanillin and ethyl vanillin

Iso- Acetovanillon (3- hydroxy-4- methoxyacetophenone ) is also a structural relative and differs from isovanillin by replacing the aldehyde group to an acetyl group. The structure corresponds to the analogy. Between vanillin and Acetovanillon

Use

Isovanillin serves as a synthetic building block, especially in the pharmaceutical, cosmetic, agricultural and food sector.

CAS registry number PubChem Dangerous Substances Directive (67/548/EEC) Formylation reaction Dichloromethyl methyl ether Negative pressure Iron(III) chloride Digital Object Identifier Chemical Research in Toxicology Tetrahedron (journal) Tetrahedron Letters
13371
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