Vanillin

• 4 -hydroxy-3 -methoxybenzaldehyde
• FEMA 3107
• Vanillaldehyd
• Vanillinum

Colorless, smelling of vanilla needles

Fixed

1.06 g · cm -3 ( 20 ° C)

82 ° C

• 285 ° C ( in a CO2 atmosphere )
• 154 ° C (13 hPa)

7.40 (25 ° C)

• Poorly in water (10 g · l-1 at 25 ° C)
• Well in ethanol and diethyl ether

Attention

Template: Infobox chemical / molecular formula search available

Vanillin (4- hydroxy-3- methoxybenzaldehyde, FEMA 3107 ) is the main flavoring in the capsular fruits of the spice vanilla (Vanilla planifolia ), and a natural flavoring substance. It is an organic chemical compound with the molecular formula C8H8O3. It is a derivative of benzaldehyde having an additional hydroxyl and a methoxy group.

Vanillin is the main component of natural Vanilla extract, a mixture of several hundred different compounds. Due to the scarcity and expense of natural vanilla extract, there has long synthetic manufacturing process for vanillin. The first commercial synthesis of vanillin began with the more readily available natural compound eugenol. Today is either vanillin synthesized from guaiacol or produced from lignin, a constituent of wood and by-product of the paper industry.

Vanillin is quantitatively the most important flavoring world, which also can be produced inexpensively. It is used in foods, beverages, ice cream, baked goods and chocolate, as well as in the perfume and pharmaceutical industries. Also, the typical smell of old paper is due in part to the vanillin in the lignin.

• 5.1 Physical Properties
• 5.2 Chemical Properties

History

Vanilla was cultivated as a flavoring by pre-Columbian peoples of Central America; at the time of their conquest by Hernán Cortés, the Aztecs used it as a flavoring for chocolate. The Europeans became known around 1520, both chocolate and vanilla.

Vanillin was first isolated in 1858 as a relatively pure substance by Nicolas- Theodore Gobley, this was done by completely evaporating a vanilla extract followed by recrystallization from hot water. In 1874, for the first time, the chemist Wilhelm Haarmann, together with Ferdinand Tiemann in Holzminden the production of vanillin from coniferin that occurs in the beef juice of softwoods ( conifers ).

1876 ​​Karl Ludwig Reimer synthesized for the first time from guaiacol ( 1) vanillin (2). In the synthesis was later named as Reimer - Tiemann reaction of guaiacol is converted in an alkaline medium with chloroform. It reacts first with chloroform of the base to dichlorocarbene. This attaches to the phenolate anion of guaiacol.

Occurrence

Vanillin is most often found in the most incorrectly referred to as pods capsule fruits of the spice vanilla (Vanilla planifolia ) ( 1.5-4 %), and also in Styrax, cloves and other plants. The freshly harvested green seed pods contain vanillin in the form of its β -D - glucoside Vanillosid, the green pods do not have the taste or smell of vanilla. Relatively pure vanillin may be deposited as a white dust or " frost " on the outside of the sleeves.

In lower concentrations, vanillin contributes to the flavor and aroma of food in various ways with: in olive oil, butter, raspberry and lychee fruits. Upon maturation of wines and spirits in oak barrels vanillin also contributes to the flavor profile. In other foods produced by heat treatment vanillin from other existing ingredients. In this way, vanillin contributes to the flavor and aroma of roasted coffee, also in maple syrup and whole grains, including corn tortillas and oatmeal.

Biosynthesis

Vanillin is a product of the Shikimisäurewegs (1). The final products of chemical reactions of this pathway are the amino acids phenylalanine, tyrosine and tryptophan. Phenylalanine (2) is converted into cinnamic acid (3) biosynthetically using the enzyme phenylalanine - ammonia - lyase (PAL) with the liberation of ammonia (NH3). This is the first step in the biosynthesis of phenylpropanoids.

Two main routes are run in discussion, as based on Phenylpropanoidverbindungen the steps to vanillin: the Ferulasäureweg and Benzoatweg. Both are first of a p -hydroxylation of cinnamic acid to p- coumaric acid (4- hydroxycinnamic acid ) (4) of. Followed by three reaction steps, their order is different, but ultimately lead to the target molecule.

• In Ferulasäureweg first a hydroxylation at the 3-position in the ring of caffeic acid (5 ), and then methylation of the ferulic acid (6), after cleavage of the double bond to give the aldehyde, vanillin (7).
• In contrast Benzoatweg carried out the cleavage of the double bond to the 4 -hydroxybenzaldehyde (8 ) and then the hydroxylation at the 3- position on the ring for the protocatechualdehyde (9) and finally to their methylation vanillin (7).

The hydroxylation from 3 to 4 and from 8 after 9 catalyzed by enzyme diphenolase. The diphenolase acts in the latter reaction as monophenol; this activity currently has a different EC number ( EC 1.14.18.1 ), but it is the same enzyme.

Production and representation

Natural sources

The up to 30 cm long fruit capsules of Vanilla planifolia are harvested just before ripening. These have not been the typical aroma and flavor of the finished product. To obtain the fruits of the so-called black tanning undergo. First, the capsule fruit is hot water or steam- treated, then followed by a fermentation in airtight containers. By drying and fermentation processes, the β -D - glucosides of vanillin transform into vanillin and glucose.

A large part of the vanillin is recovered from the resulting in papermaking Sulfitabfällen. The ligninsulfonic acid contained therein is treated at elevated temperature and pressure with oxidant and alkali, in which is formed, inter alia, vanillin, which is purified by extraction, distillation and crystallization. The yields are 7-25 % depending on the type of wood. This artificial vanilla flavor on lignin - base has a richer flavor profile. This is due to the presence of lignin - derived product as Acetovanillon - a contaminant that does not occur from a Guajacolsynthese to vanillin.

Technical syntheses

• Vanillin can be gained to isoeugenol ( 2) with alkalis and subsequent oxidation by potassium permanganate or ozone technically by isomerization of eugenol (1).

• A synthesis is carried out on a laboratory scale by electrophilic bromination of 4 -hydroxybenzaldehyde (1) for 3-bromo -4-hydroxybenzaldehyde (2), followed by copper -catalyzed methoxylation of vanillin (3):

• By means of the Vilsmeier -Haack synthesis obtained vanillin from guaiacol in about 70 % yield.
• Guaiacol can be with formaldehyde and 3- nitrobenzene sulfonic acid in a process which takes several days to vanillin and metanilic convert.
• Another option is the substitution reaction of guaiacol (1) with glyoxylic acid and then oxidizing the VMA (2) formed of 4 - hydroxy-3- methoxyphenylglyoxylsäure (3), which is decarboxylated to vanillin (4).

Biotechnological methods

Alternatively, biotechnological methods are available. Vanillin can be produced for example by Amycolatopsis and Streptomyces strains from ferulic acid. The ferulic acid can also engineered with the help of Pseudomonas strains from eugenol in the fed- batch process (eugenol is toxic to the cells ) are produced. Eugenol is a readily available raw material and comes from clove oil. In contrast to chemical manufacturing ( "nature- identical" ), vanillin bioengineered may be declared as "natural."

Properties

Physical Properties

Vanillin occurs as colorless, characteristic sweet -smelling needles, which gradually oxidize in moist air to vanillic acid. It dissolves poorly in water (10 g / l at 25 ° C), however, well in ethanol and diethyl ether. It melts at 82 ° C and boils at 285 ° C. at atmospheric pressure in a CO2 atmosphere and 154 ° C under reduced pressure ( 13 hPa). It crystallizes in the monoclinic crystal system and four formula units per unit cell.

Chemical Properties

The substance structurally derived from both the benzaldehyde and from guaiacol (2- methoxyphenol ). Because of its bifunctional character vanillin is very reactive. By etherification, esterification or aldol condensation very many derivatives are synthesized. Upon attack on the aromatic ring, further reactions are possible. Catalytic hydrogenation of vanillin to vanillyl alcohol, or leads to 2 -methoxy-4 -methylphenol. Vanillin can be enzymatically oxidized to vanillic acid. An aqueous solution of iron ( III ) chloride is a violet blue color with vanillin.

The pKa of the phenolic OH group is 7.40 (25 ° C). This value is compared with the phenol with 9.99 significantly lower; the aldehyde is increased by electron-withdrawing its - M effect of the OH acidity; the phenolic OH bond is increasingly polarized. The pKa value of 4- hydroxybenzaldehyde moves at a similar value and amounts to 7.66; the missing methoxy group makes little difference here from; and the guaiacol (2- methoxyphenol ) has with its pKa value of 9.98 is virtually no difference to the phenol.

Isomers and structural Related

Isovanillin ( 3-hydroxy -4-methoxybenzaldehyde ) is an isomer and differs from 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.

Ortho- vanillin (2- hydroxy-3- methoxybenzaldehyde ) is also an isomer and differs from vanillin by the position of the hydroxy group. The prefix ortho identifies here the position of the hydroxyl group with respect to the aldehyde group; vanillin in these two groups are in the para position.

Ethyl vanillin (4- hydroxy-3- ethoxybenzaldehyde ) is a structural relatives and differs from vanillin by replacing the methyl group to an ethyl group. It does not come naturally, but is made of synthetic material. Today it is often used as artificial flavoring vanillin instead of the more expensive, as it is also 2-4 times more intense in flavor and aroma.

Acetovanillon (4- hydroxy-3- methoxyacetophenone, and apocynin ) is also a structural relative and differs from vanillin by replacing the aldehyde group to an acetyl group. It arises in artificial vanilla flavors on lignin - based.

Vanillin and ethyl vanillin have a similar smell, the Isovanillins, however, is hardly noticeable. Vanillin and ethyl vanillin can be readily separated by thin layer chromatography with mixtures of hexane and ethyl acetate.

Use

Vanillin is quantitatively the most important flavoring world, because it can be produced inexpensively. It is a consumption of 15,000 tons per year of ( 2004). The approximately 2,000 tons of fruit capsules real vanilla, which are harvested annually worldwide, only contain about 40 tonnes of vanillin.

Vanillin, for example in admixture with vanilla sugar (according to ISO standard 5565-2 v. 1999, the amount of vanillin from 1.6 to 2.4 %) were sold and used as a flavoring agent in foods, including ice cream, baked goods and chocolate. In addition, vanillin is one of many fragrances in perfumery and to improve the taste of pharmaceuticals and vitamin preparations, where it is used in small quantities to round off and fixation of sweet, balsamic scent.

In the chemical industry vanillin is used for example as starting material or intermediate in the synthesis of various drugs such as levodopa, methyldopa, and papaverine. It is also part of Günzburg reagent - an alcoholic solution of phloroglucinol and vanillin for the detection of the free hydrochloric acid in the gastric juice.

Vanillin may be used as a detection reagent for the derivatization of compounds in thin layer chromatography. The developed plate is wetted and heated by spraying or dipping with a vanillin. Some compounds exhibit this characteristic color reactions by which they can be identified.

Further reactions and enzymes

• Vanillin dehydrogenase - enzyme that catalyzes vanillin to vanillic
• Vanillin synthase - catalysis
• Vanillyl-alcohol oxidase - enzyme that catalyzes various phenolic compounds by oxidation
• Vanillate monooxygenase - catalysis of vanillate to protocatechuic