Alcohols and Carbonyl Compounds

At a level of 1 ppb (767) (Z)-4-heptenal (5) confers a creamy flavor 220) to deodorized butter oil. At higher concentrations (from 2 ppm) this aldehyde causes rancidity in butter (22) and soybean oil 560). 

Furthermore, aldehyde (5) contributes to the off-flavor in frozen stored cod Gadus morlina) 368). ( )-4-Heptenal (6) which has an aggressive putty and green odor constitutes the offensive pheromone of the tropical bedbug species [black Hemiptera-hug (PentatomideaJ] 398). 

The three aliphatic C-8 compounds (8), (9) and (11) constitute the main components of the raw potato flavor (76). The two alcohols (8) and (11) are also present in flavor concentrates of raw mushrooms of the genus 

Agaricus bisporus and Boletus edulis 682), In addition, ketone (10) is found in the volatile parts of cooked mushrooms 473), 

The importance of 2-alkanones of different chain length in the flavor of dairy food has been fully recognized 103, 159, 160, 161), Oil of rue Ruta graveolens L.) consists almost completely of methyl 

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The use of the enolsilyl ether of 1-menthone [16, 19, 21-23] and of some free triflic acid favors the formation of the thermodynamically controlled products as with free 2,2 -dihydroxydiphenyl [22] and only subsequently added HMDS 2 [22]. On reacting silylated alcohols and carbonyl compounds with pure trimethylsilyl triflate 20 under strictly anhydrous conditions no conversion to acetals is observed [24]. Apparently, only addition of minor amounts of humidity to hydrolyze TMSOTf 20 to the much stronger free triflic acid and hexamethyldisiloxane 7 or addition of traces of free triflic acid [18-21, 24, 26] or HCIO4 [25] leads to formation of acetals. 

Oxygenates were recovered from the Fischer-Tropsch aqueous product, employing a separation strategy similar to that in the Sasol 1 refinery. The main difference was in volume, and this made further separation of the different alcohols and carbonyl compounds worthwhile. Some of the ethanol served as a blending component in motor gasoline, with the final blend containing around 10% ethanol.38 Most of the alcohols and carbonyl compounds were sold as chemicals. In addition to the oxygenates, the C2 hydrocarbons were also recovered and sold. 

Under the action of heat and free radicals, hydroperoxides are decomposed into alcohols and carbonyl compounds. The primary hydroperoxide RCH2OOH is an unstable molecule and is decomposed into aldehyde, acid, and dihydrogen through the interaction with formed aldehyde [111]. 

Consistent with the direct observation of the emissions are field measurements in remote areas. For example, Fehsenfeld et al. (1992) measured the composition of VOC at two rural locations in the United States, summarized in Fig. 6.27. Alcohols and carbonyl compounds comprise 40-70% of the total. Of these, a significant portion appear to be direct emissions, with methanol being a major contributor to the oxygen-containing portion. Similarly, Singh et al. (1995) re-... 

Reaction of Carbon Atoms with Alcohols and Ethers. The electro-philicity of atomic carbon and the exothermicity of carbon monoxide formation in its reactions facilitates attack on, and removal of oxygen by C atoms. Deoxygenation of ethers, alcohols, and carbonyl compounds has been reported. This process is generally a highly exothermic reaction, which is likely to generate products with excess energy. 

The fruit of the cucumber plant Cucumis sativus) is mainly eaten raw or as pickle. Approximately 30 volatile compounds have been detected in the volatile fraction of cucumber, with aliphatic alcohols and carbonyl compounds being most abundant [35]. Fresh cucumber flavour develops as a result of enzymatic degradation of linoleic and linolenic acid rapidly after the tissue is disrupted (Scheme 7.2), by which ( ,Z)-2,6-nonadienal and ( )-2-nonenal mainly are formed [184]. ( ,Z)-2,6-Nonadienal is the main flavour volatile of cucumber fruit, with ( )-2-nonenal as the second most important compound (Table 7.7) [185, 186]. 

The fruit of pumpkin (Cucurbita pepo) is eaten boiled or baked. About 30 compounds have been identified in the volatile extracts of raw pumpkin, with the major classes of compounds being aliphatic alcohols and carbonyl compounds, furan derivatives and sulfur-containing compounds. Hexanal, ( )-2-hexenal, (Z)-3-hexen-l-ol and 2,3-butanedione have been identified as important for the flavour of freshly cooked pumpkins (Table 7.7) [35] however, studies using GC-O techniques are needed to get a better understanding of the character-impact compounds of pumpkins. 

Noyori, R., Yamakawa, M. and Hashiquchi, S. Metal-Ligand Bifunctional Catalysis A Nonclassical Mechanism for Asymmetric Hydrogen Transfer between Alcohols and Carbonyl Compounds. J. Org. Chem. 2001, 66, 7931-7944. 

Equations (9.4) and (9.5) illustrate termination reactions. Depending on the structure of the alkyl group, disproportionation to alcohols and carbonyl compounds may take place ... 

Some reagents, such as Se02 (the best oxidant for allylic hydroxylation) and palladium(II) (best known for oxidation of alkenes to allylic alcohols and carbonyl compounds), can be used in the formation of cc,p-unsaturated carbonyl compounds under special reaction conditions.671,692... 

The major substrate is ethanol, but it deals successfully with many other alcohols and carbonyl compounds. The mammalian enzyme was first crystallized by Bonnichsen and Wassdn from horse liver in 1947,1341 but only in the past 15 years has complete structural information been obtained by determination of the complete amino acid sequence and X-ray structure. 

In contrast to halides, alcohols, and carbonyl compounds, hydrocarbons may be extremely difficult to racemize. This is particularly true for a compound with a quaternary asymmetric center, such as methylethylpropylbutylmethane, 28, which has no handle to allow one to convert the asymmetric carbon to a symmetric condition by simple chemical means ... 

Nicotinamide coenzymes act as intracellular electron carriers to transport reducing equivalents between metabolic intermediates. They are cosubstrates in most of the biological redox reactions of alcohols and carbonyl compounds and also act as cocatalysts with some enzymes. 

At the beginning of the 20th century, Meerwein,1 Ponndorf2 and Verley3 showed that alcohols and carbonyl compounds can equilibrate as in Equation below under the action of Al3+ alkoxides. 

Electrophilic ring closure of aryl-substituted compounds such as alkenes, halides, alcohols, and carbonyl compounds called cyclialkylation can be induced by conventional Friedel-Crafts catalysts309 and by superacids. Examples are also known in which an intermolecular alkylation step is followed by intramolecular alkylation of the intermediate to furnish a cyclic product. 

Oxygenation of 2-substituted adamantanes with methyl(trifluoromethyl)dioxirane showed a reaction constant, p = -2.31, consistent with a strongly electron-demanding transition state. Analysis of the effect of solvents on the rate yielded a positive regression coefficient with Dimroth-Reichardt Ej solvent polarity parameter. A mechanism involving an electrophilic O atom insertion has been postulated for the formation of alcohols and carbonyl compounds.201... 

Although it appears that only a small amount of aluminum isopropoxide is required to catalyze the equilibrium between the alcohol and carbonyl compound, in practice it usually is desirable to employ an excess of the reagent. As the equation indicates, one mole of isopropoxide will reduce directly three moles of carbonyl compound. 

The survey in Figure 9.23 shows that N nucleophiles can react with carbonyl compounds in the following ways (1) An addition to the C=0 double bond followed by an SN1 reaction leads to the formation of AW-acetals (details Section 9.2.4). (2) An addition to the C=0 double bond is followed by an El reaction by which, amongst others, enamines are formed (details Section 9.3). (3) Imines are produced. We still need to discuss whether the reaction of O nucleophiles with carbonyl compounds also gives us two options—parallel to the two possibilities (1) and (2) mentioned above. According to Figure 9.12 alcohols and carbonyl compounds always afford 0,0-acetals—through an addition and an SN1 reaction (details Section 9.2.2). 

REACTIONS WITH ALCOHOLS AND CARBONYL COMPOUNDS 5.2.1 Alcohols and silyl ethers... 

Iodosylbenzene Reactions with Unsaturated Compounds. Reactions with Alcohols and Carbonyl Compounds. Reactions with NitrogenCompounds. Reactions with Sulfur and Other Compounds. 

In addition to the somewhat comprehensive treatment of alcohols and carbonyl compounds, the carboxylic acids can also play a role in the sensory properties of packaging materials. Because of their very low volatility their contribution is mainly to the taste of aqueous solutions. 

Oxazolidines are commonly prepared from /3-amino alcohols and carbonyl compounds (equation 173). The condensation is conveniently conducted in boiling benzene with continuous removal of water. Treatment of 2-aminoethanol with formaldehyde yields the parent compound (67BSF571). An interesting reaction is the formation of the enantiomerically pure oxazolidine (307) from (-)-ephedrine and the alkynic sulfone PhS02C=CMe (79JCS(P1)1430). 

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