Reaction aroma

Aldehydes fiad the most widespread use as chemical iatermediates. The production of acetaldehyde, propionaldehyde, and butyraldehyde as precursors of the corresponding alcohols and acids are examples. The aldehydes of low molecular weight are also condensed in an aldol reaction to form derivatives which are important intermediates for the plasticizer industry (see Plasticizers). As mentioned earlier, 2-ethylhexanol, produced from butyraldehyde, is used in the manufacture of di(2-ethylhexyl) phthalate [117-87-7]. Aldehydes are also used as intermediates for the manufacture of solvents (alcohols and ethers), resins, and dyes. Isobutyraldehyde is used as an intermediate for production of primary solvents and mbber antioxidants (see Antioxidaisits). Fatty aldehydes Cg—used in nearly all perfume types and aromas (see Perfumes). Polymers and copolymers of aldehydes exist and are of commercial significance. 

T. E. Stewart, M Survey of the Chemistry of Amino Acids-Reducing Sugar Reaction in Relation to Aroma Production, Scientific and Technical Surveys No. 61, British Eood Manufacturing Industries Research Association, London, Dec. 1969. 

A number of other valuable aroma chemicals can be isolated from essential oils, eg, eugenol from clove leaf oil, which can also, on treatment with strong caustic, be isomerked to isoeugenol, which on further chemical treatment can be converted to vanillin (qv). Sometimes the naturally occurring component does not requke prior isolation or concentration, as in the case of cinnamaldehyde in cassia oil which, on dkect treatment of the oil by a retro-aldol reaction, yields natural ben2aldehyde (qv). This product is purified by physical means. 

From West Indian lime oil, a trace low Foiling constituent, 1-methyl-1,3-(or 1,5 /74< 5 -3 7- -cyclohexadiene has been characterized (27). This compound, which possesses an intense and characteristic lime aroma, was later confirmed to be the 1,3-isomer [1489-56-1] (11). This compound can easily be made in a biomimetic way through the reaction of citral [5392-40-5] (3,7-dimethyl-2,6-octadienal) with citric acid (28,29). 

Most aroma chemicals are relatively high boiling (80—160°C at 0.4 kPa = 3 mm Hg) Hquids and therefore are subject to purification by vacuum distillation. Because small amounts of decomposition may lead to unacceptable odor contamination, thermal stabiUty of products and by-products is an issue. Important advances have been made in distillation techniques and equipment to allow routine production of 5000 kg or larger batches of various products. In order to make optimal use of equipment and to standardize conditions for distillations and reactions, computer control has been instituted. This is particulady well suited to the multipurpose batch operations encountered in most aroma chemical plants. In some instances, on-line analytical capabihty is being developed to work in conjunction with computer controls. 

Linalool has been used to prepare a mixture of terpenes useful for enhancing the aroma or taste of foodstuffs, chewing gums, and perfume compositions. Aqueous citric acid reaction at 100°C converts the linalool (3) to a complex mixture. A few of the components include a-terpineol (34%) (9), Bois de Rose oxide (5.1%) (64), ocimene quintoxide (0.5%) (65), linalool oxide (0.3%) (66), tij -ocimenol (3.28%) (67), and many other alcohols and hydrocarbons (131). 

Garyophyllene. (-)-CaryophyUene can be isolated from Indian turpentine and has been used to prepare a number of woody aroma products. The epoxides are produced by reaction with peracids. Acetylation of caryophyUene also gives a usehil methyl ketone (180) (Fig. 8). Acid-catalyzed rearrangement of caryophyUene in the presence of acetic acid gives a mixture of esters, which are related to caryolan-l-ol and clovan-2-ol (181). 

Longifolene. There are at least four commercially important aroma chemicals made from (+)-1ongifo1ene and about thirteen products made from (-)-isolongifolene (90) (182). Acetoxymethyl longifolene or the formate are formed during the Prins reaction on (+)-1ongifo1ene. Saponification of the esters gives the useful perfumery alcohol (183) (Fig. 9). 

Alcohohc beverages are made up primarily of ethanol, congeners, and water. Congeners are vaporized with the alcohol in distillation below 190° proof and are developed during the maturation process by oxidation and other reactions. These components contribute to palatability and create the characteristic appearance, aroma, and taste of a particular spidt. When the spirit is distilled at a lower proof, more congeners are present and the spirits possess more character. Congeners are usually reported either as grams per 100 Hters at "as is" proof, or as 100° proof at parts per million or parts per billion. 

The two isomeric butanals, n- and isobutyraldehyde, C HgO, are produced commercially abnost exclusively by the Oxo Reaction of propylene. They also occur naturally ia trace amounts ia tea leaves, certain oils, coffee aroma, and tobacco smoke. 

Methylpyrazine reacts with sodamide in liquid ammonia to generate the anion, which may be alkylated to give higher alkylpyrazines (Scheme 10) (61JOC3379). The alkylpyrazines have found extensive use as fiavouring and aroma agents (see Section 2.14.4). Condensation reactions with esters, aldehydes and ketones are common, e.g. methyl benzoate yields phenacylpyrazine in 95% yield, and reactions of this type are summarized in Scheme 11. 

Carotenoids are present at low levels in tea leaf.60 Neoxanthin, violaxanthin, lutein, and B-carotene are the major components of this group. They enter into reactions that lead to aroma formation.61... 

It has been suggested that enzymic reaction of leucine during processing could lead to the formation of desirable aroma components and that these reactions would be varied during periods of climatic stress when the... 

Example 5.4 Benzyl acetate is used in perfumes, soaps, cosmetics and household items where it produces a fruity, jasminelike aroma, and it is used to a minor extent as a flavor. It can be manufactured by the reaction between benzyl chloride and sodium acetate in a solution of xylene in the presence of triethylamine as catalyst9. 

Ho C-T (1996) Thermal degradation of Maillard aromas. In Ikan R (ed) the Maillard reaction Consequences for the chemical and life sciences. Wiley, Chichester, UK, pp 27-53... 

The distinctive aroma of ammonia is often apparent in bakeries but not in the final product. Bakers yeast performs its leavening function by fermenting such sugars as glucose, fructose, maltose, and sucrose. The principal products of the fermentation process are carbon dioxide gas and ethanol, an important component of the aroma of freshly baked bread. The fermentation of the sugar, glucose—an example of a decomposition reaction — is given by the equation in Fig. 5.19.1. 

Moody and coworkers have employed a biomimetic hetero-Diels-Alder-aroma-tization sequence for the construction of the 2,3-dithiazolepyridine core unit in amythiamicin D and related thiopeptide antibiotics (Scheme 6.243 a) [426]. The key cycloaddition reaction between the azadiene and enamine components was carried out by microwave irradiation at 120 °C for 12 h and gave the required 2,3,6-tris(thi-azolyl)pyridine intermediate in a moderate 33% yield. Coupling of the remaining building blocks then completed the first total synthesis of the thiopeptide antibiotic... 

In addition to bacterial conversion of L-methionine to cheese aroma compounds, certain cheese-ripening yeasts have been implicated. They include De-baromyces hansenii, Geotrichum candidum, and Yarrowia lipolytica, in addition to Kluyveromyces lactis and Saccharomyces cerevisiae (previously noted). Of these yeasts, Geotrichum candidum was most effective at producing sulfur compounds with the major product being S-methyl thioacetate, with smaller amounts of MT, DMS, DMDS, and DMTS. Kluyveromyces lactis had a similar profile, but produced a much smaller amount of S-methyl thioacetate than did G. candidum. S-Methyl thioacetate is formed by a reaction of MT and acetyl-CoA (Equation 7) ... 

P-parinaric acid, physical properties, 5 33t P-pentenoic acid, physical properties, 5 3 It P-peroxylactones, 18 484 Beta phase titanium, 24 838 in alloys, 24 854-856 properties of, 24 840, 941 P-phellandrene, 24 493 P-picoline, 21 110 from acrolein, 1 276 uses for, 21 120 P-pinene, 3 230 24 496-497 major products from, 24 478 /-menthol from, 24 522 as natural precursor for aroma chemicals, 3 232 terpenoids from, 24 478-479 P-propiolactone, polymerization of, 14 259 P-quartz solid solution, 12 637—638 Beta ratio, in filtration, 11 329—330 Beta (P) rays, 21 285 P-scission reactions, 14 280-281 P-skytanthine, 2 101 P-spodumene solid solution, 12 638-639 P-sulfur trioxide, 23 756 P-sultones, 23 527 P-tocopherol, 25 793 P-tocotrienol, 25 793 P-vinylacrylic acid, physical properties, 5 33t... 

The suitability of ethers derived from 1,4-dihydroxy-1,2,3,4-tetrahydro-naphthalene (DHTN) in the design of polymers susceptible to catalyzed thermolytic cleavage is demonstrated by the behavior of its bis-p-nitrophenyl ether derivative upon treatment by a trace of acid. Figure 2, curve A, shows the H-NMR spectrum of the starting compound, while curve B shows the product which is obtained upon addition of triflic acid. It is readily seen from these spectra that quantitative cleavage into naphthalene and p-nitrophenol is obtained as elimination occurs easily to afford the aromatic product. The driving force in this reaction is the facile aroma-tization which produces naphthalene. 

Benzophenone, directed reaction with acetaldehyde, 50, 68 1,4-Benzoquinone, 2,3-dichloro-5,6-dicyano-, (DDQ), aroma-tization with, 54, 14 Benzoylacetone, from acetophenone and acetic anhydride,... 

The spectra were recorded in the positive-ion mode in the range of m/z 120-1 500. Some chromatograms illustrating the effect of aldehydes on the interaction of mv3gl and B2-3 -gallate are shown in Fig. 2.120. The chromatograms demonstrate that different aldehydes influence differently the formation of anthocyanin-flavanol pigments. The results of HPLC-MS measurements are compiled in Table 2.94. Because free aldehydes display an unpleasant aroma in Port wine these reactions may improve the quality of wines and contribute to the colour formation [266],... 

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