Methyl ester

Methyl ester of a carboxylic acid. The methyl ester residue is marked in blue . R stands for a hydrogen atom or an organyl radical (alkyl radical, aryl radical or alkylaryl radical, etc.). In chloroformate
methylester R is a chlorine atom.

Dimethyl ester (top) and monomethyl ester (bottom) of carbonic acid. The functional group is marked in blue .

Methyl ester of a sulfonic acid. The methyl ester residue is marked in blue . R stands for an organyl radical (alkyl radical, aryl radical or alkylaryl radical, etc.).

Methyl esters are chemical compounds that belong to the group of carboxylic acid esters . They are created by esterifying a carboxylic acid with methanol . They have the characteristic functional ester group . In a broader sense, the methyl esters also include carbonic acid esters and esters derived from sulfonic acids and methanol. Similarly, methyl esters in the broader sense can also form from nitric acid , sulfinic acids , phosphonic acids or phosphinic acids on the one hand and methanol on the other.

Occurrence

Carboxylic acid methyl esters come as so. Fruit esters are found in many fruits and dishes as an odor-giving component. In nature, methyl cinnamate occurs in various plants, e.g. B. in strawberries and different types of basil . The eucalyptus species Eucalyptus olida has the largest amount of cinnamic acid methyl ester.

Anthranilic acid methyl ester occurs naturally in cocoa, coffee, grapes, grapefruit, jasmine, lemons, limes, strawberries and mandarins as well as in many flower oils (e.g. neroli , ylang-ylang oil ).

Manufacturing

Methyl esters arise z. B. from a carboxylic acid and methanol with acid-catalyzed dehydration. Methyl esters can also be obtained from carboxylic acid chlorides and methanol by the Schotten-Baumann method . Methyl esters can also be synthesized from carboxylic acid anhydrides and methanol . The nucleophilic substitution of methyl halides (e.g. methyl iodide ) with carboxylate ions produces methyl esters, as does the reaction of carboxylic acids with diazomethane , CH ₂ N ₂ .

Similarly, dimethyl esters are formed from dicarboxylic acids and methanol, trimethyl esters from tricarboxylic acids and methanol, etc.

use

Some methyl esters of carboxylic acids are used as flavoring and aromatic substances:

• Fruit flavors:
  • Butyric acid methyl ester smells like pineapple or apple
  • Phenylacetic acid methyl ester Aroma of honey

• Spice Flavors:
  • Benzoic acid methyl ester smells like niobe oil

Methyl esters of fatty acids ( fatty acid methyl esters ) are used as biodiesel or as an additive to conventional diesel fuel. In order to convert the rapeseed oil ( glycerol ester of long-chain fatty acids ) into biodiesel ( FAME , rapeseed oil methyl ester , soybean oil methyl ester ), the rapeseed oil has to be transesterified , i.e. the glycerol part of the ester has to be replaced by methanol. 4-Hydroxybenzoic acid methyl ester (PHB ester) is used as a preservative E 218 in the food industry.

See also

• Ethyl ester , Carbonsäureester which are derived from ethanol derived

Individual evidence

1. ↑ Wolfgang Legrum: Fragrances, between stink and fragrance , Vieweg + Teubner Verlag (2011) pp. 85–86, ISBN 978-3-8348-1245-2 .
2. ↑ Amparo Viña, Elizabeth Murillo: Essential oil composition from twelve varieties of basil (Ocimum spp) grown in Colombia , in: J. Braz. Chem. Soc. , 2003 , 14  (5); doi : 10.1590 / S0103-50532003000500008 .
3. ↑ DJ Boland, JJ Brophy, APN House, Eucalyptus Leaf Oils , 1991, ISBN 0-909605-69-6 .
4. ↑ Data sheet Methyl anthranilate, natural (US), ≥ 98%, FG from Sigma-Aldrich , accessed on April 9, 2012 ( PDF ).
5. ^ K. Peter C. Vollhardt: Organic Chemistry , VCH, Weinheim 1990, ISBN 3-527-26912-6 , p. 772.