Pyrazine, 2-ethyl-3,5-dimethyl

Table II lists the major volatile compounds from baked blanched and fried blanched shallot slices generated from thermal degradation of nonvolatile flavor precursors of shallot were methyl propyl trisulfide, dimeihylthiophencs, methyf propyl disulfide, and dipropy trisulfide. The major volatile compounds that were probably generated from ihemia imeractiuns of nonvolatile flavor precursors of shallot and sugars were pyrazines, especially ethyl dimethyl pyrazines, dimethyl-pyrazines, ethyl methyl pyrazines, and trimethylpyrazine.

Fluorobenzene to fluorodihydrocatechol and fluorocatechol Conversion of 2,5-dimethyl pyrazine to 5-metyl pyrazine-2-carboxylic acid, conversion of 5-ethyl-2-methyl pyridine to... 

Pyrazine, 2-ethyl-3-5-dimethyl Lf Pyrazine, 2-ethyl-3-6-dimethyl Lf Pyrazine, 2-ethyl-5-methyl Lf ... 

Pyrazine, 2-ethyl-3-methyl Sd (roasted) ° Pyrazine, 2-ethyl-5-methyl Sd (roasted) ° Pyrazine, 2-ethyl-6-methyl Sd (roasted) ° Pyrazine, 3-5-dimethyl-2-(2 -furyl) Sd Pyrazine, 3-5-dimethyl-2-acetyl Sd Pyrazine, 3-6-dimethyl-2-(2 -furyl) Sd Pyrazine, 3-6-dimethyl-2-acetyl Sd Pyrazine, 3-ethyl-2-5-dimethyl Sd (roasted) " ... 

Pyrazine, 3-ethyl-2-6-dimethyl Sd (roasted) ° Pyrazine, 3-ethyl-2-methyl Sd Pyrazine, 3-methyl-2-(2 -furyl-4 -methyl) ... 

Trimethyl pyrazine 3-ethyl 2,5-dimethyl pyrazine FIG. 8 Flavor compounds in roasted flaxseed observed by Meyers et al. (2004). 

The odor threshold of the pyrazines range from 0.006 ppb in water for 2—propyl—3-methoxypyrazine (29) to 43 ppm in water for 2,5—dimethyl—3-ethyl pyrazine (30). A excellent review of the pyrazines found in food products has been prepared by Maga (31). 

In Figure 3, as in Figure 2, samples isolated from oats with 7.4% and 8.3% lipid content were different with regard to chemical composition. Since the oil itself may play several roles, for example as generator of aroma compounds as well as solvent for other volatile compounds, it is of interest to follow the aroma pattern in the abovementioned samples. The amount of heterocycles decreased in most cases when the initial oat lipid content increased. Compounds such as pyrazine derivatives (methyl, 2,5-dimethyl, 2,6-dimethyl, 2-ethyl-5-methyl, trimethyl, 2,5-methyl-3-ethyl), furfural, 5-... 

N-Heterocycles Pyridine Pyrazines Unsubstituted, 2,3-Dimethyl, MARM ++ 2,5-Dimethyl-3-ethyl, Methyl, 2-Ethyl-6-methyl, 2,5-Dimethyl, 2-Ethyl-5-methyl, 2,6-Dimethyl, Acetylmethyl, 2-(2-Furyl), Ethyl, 2-Methyl-5-(methylethyl), Trimethyl Pyrroles 2-Acetyl, N-Methyl-2-furyl, 1-Formyl, 1-Furfury 1-2-formyl, 5-Methvl-2-formvl Trimethylpyrazine (TMPy) (RV = 0.989)... 

A maltol-ammonia browning reaction produced thirteen pyrazines, two pyrroles, two oxazoles, and one pyridine (12). The major products of this system were 2-ethyl-3-hydroxy-6-methylpyridine and 2-ethyl-3,6-dimethylpyrazine. It is difficult to construct possible formation mechanisms for these compounds from maltol and ammonia. All the carbon atoms must come from maltol. It is possible, then, that maltol degrades into smaller carbon units and that these fragments recombine to form larger carbon units, producing these compounds. Recently, the formation of thiophenones and thiophenes from the reaction of 2,5-dimethyl-4-hydroxy-3(2H)-furanone and cysteine or cystine was reported (13. 14). All these reaction mixtures were reported to possess a cooked meat-like flavor. 

The Strecker reactant, i.e., the a-dicarbonyl, picks up ammonia during the Strecker reaction and can then form heterocyclic volatiles, particularly pyrazines. The most powerful odorants among these are the 2-ethyl-3,5-dimethyl- (0.04) and the 2,3-diethyl-5-methyl-derivatives (0.09). It is worth noting that most other alkylpyrazines have much higher thresholds and thus make relatively little contribution to the aroma of heated foods. 

The continuous vapor phase dehydrogenation of piperazines is effectively carried out over a prereduced 80% CuO-20% Cr2Os catalyst at 350°. In this way 2-ethyl-, 2,6-dimethyl-, and 2,3,5,6-tetramethylpiperazines have been converted into the corresponding pyrazines in 79-89% yield.126-128 Pyrazine itself is obtained from piperazine in 18% yield by the use of 5% Pt on alkali-washed firebrick catalyst.129 The catalytic deamination of diethylenetriamine over alumina-based catalysts at temperatures of 300°-400° gives good... 

Dimethyl-188 and 2,6-dimethylpyrazine react very similarly to methylpyrazine. Thus, 2,6-dimethylpyrazine can be converted into a monoanion with sodamide in liquid ammonia which can be condensed with aldehydes and ketones,179 acylated with esters,181 and alkylated with alkyl halides181 to give the corresponding 2-methyl-6-substituted pyrazines. Acylation under suitable conditions also yields diacylated derivatives. Thus, when 2,6-dimethylpyrazine, sodamide, and ethyl benzoate are reacted in 1 3 2 molecular proportion, 38% 2,6-diphen-acylpyrazine (35) and 25% 2-methyl-6-phenacylpyrazine (36) is obtained. From the preparative point of view it is better to form the diacyl derivative by the further acylation of the monoacyl derivative rather than by direct diacylation.187... 

Reactions of 3-substituted 2-(lV-phenylaminomethyl)piperazines with a slight excess of ethyl 2-chloroacetate under reflux afforded mixtures of 9-substituted 2-phenylperhydropyrido[l,2-a]pyrazin-3- and -4-ones, which could be separated by column chromatography [72JCS(P2)1374], When 2-[(3-trifluoromethylphenyl)aminomethyl]piperidine was heated with optically active ethyl 2-chloropropionate (87MIP1 91TA231), or lactic acid ethyl ester methanesulphonate (91TA231), the product was a C-9a epimeric mixture of 2-(3-trifluoromethylphenyl)-4-methylperhydropyrido[l,2-fl]-pyrazin-3-ones. The reaction between yV-methyl-2-piperidine-carboxamide and hydroxymaleic anhydride in pyridine resulted in 2,3-dimethyl-3-hydroxyperhydropyrido[l,2-a]pyrazine-l,4-dione (74CB2804). 

Amino-3-phenylisoxazol-4-yl)pyrazine (168) gave 2-phenylethynylpyrazine (169) (NaN02, AcOH—H20, 20°C, 1 h 80% mechanism suggested).795 2-(Benzo[ ]thien-2-yl)-3,6-dim ethyl pyrazine (170) underwent desulfurization to 2,5-dimethyl-3-phenacylpyrazine (171) (Raney Ni, EtOH, reflux, 8 h ... 

The remaining minor routes appear to be represented in recent literature only by the reaction of ethyl 2-pyrazinecarboxylate (67) with prelithiated dimethyl sulfoxide (DMSO) in THF at 20°C during 3 h to afford 2-(methylsulfinylacetyl)pyrazine (68) (30%) 896 and by the reaction of chloropyrazines (69) with sodium p-acetamidoben-zenesulfinate to give the corresponding p-acetamidophenylsulfonylpyrazines (70).882... 

Dimethyl-3-ethyl-2-hydroxy-E9b/2, 268f, (Gloxal + H2N-CHR-CO-NH2) 2-Hydroxy-3-isopropyl-5-methyl-E9b/2, 268f. (H3C-CO-CHO + H2N-CHR-CO-NH2) 2-Hydroxy-5(or6)-methyl-3-propyl-E9b/2, 268 f. (H3C-CO-CHO -I- H2N-CHR-CO-NH2) Pyrazin-1,4-bis-oxid 2,5-Diethyl-E9b/2, 309 (N-Oxidat.) Pyrazin-l-oxid... 

Pentafulven 6,6-Bis-[dimethyl-amino]-2-cyan- V/2c, 582 Piperidin 1-Phenylazo- X/3, 719 Pyrazin 2-Cyan-3,6-diisopropyl-E9b/2, 336 (Cl - CN) Pyrazolidin 3-Imino-l-(2-phenyl-ethyl)- X/2, 63... 

Cocoa Butter Cocoa butter is one of the most Uked and highly prized food ingredients because of its desirable flavor and unique melting behavior. As early as 1961, van Elzakker and van Zutphen (32) studied and identified 23 volatile compounds in the vacuum steam distillate of cocoa butter. Later, Rizzi (33) identified nine alkylpyrazines including methylpyrazine, 2,5-dimethylpyrazine, 2,6-dimethylpyrazine, 2,3-dimethylpyrazine, 2-ethyl-5-methylpyrazine, trimethylpyra-zine, 2,5-dimethyl-3-ethylpyrazine, 2,6-dimethyl-3-ethylpyrazine, and tetramethyl-pyrazine in the basic fraction of a vacuum steam distillate of cocoa butter. 

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