Aromatic compounds benzaldehyde

Human beings can detect and distinguish thousands of different compounds by smell, often with considerable sensitivity and specificity. Most odorants are relatively small organic compounds with sufficient volatility that they can be carried as vapors into the nose. For example, a major component responsible for the smell of almonds is the simple aromatic compound benzaldehyde, whereas the sulfhydryl compound 3-methylbutane-l-thiol is a major component of the smell of skunks. 

Bitter almonds are the source of the aromatic compound benzaldehyde. 

It should be noted that aliphatic compounds (except the paraffins) are usually oxidised by concentrated nitric acid, whereas aromatic compounds (including the hydrocarbons) are usually nitrated by the concentrated acid (in the presence of sulphuric acid) and oxidised by the dilute acid. As an example of the latter, benzaldehyde, CjHsCHO, when treated with concentrated nitric acid gives ffi-nitrobenzaldehyde, N02CgH4CH0, but with dilute nitric acid gives benzoic acid, CgHgCOOH. 

The reaction has been applied to nonheterocyclic aromatic compounds Benzene, naphthalene, and phenanthrene have been alkylated with alkyllithium reagents, though the usual reaction with these reagents is 12-20, and Grignard reagents have been used to alkylate naphthalene. The addition-elimination mechanism apparently applies in these cases too. A protected form of benzaldehyde (protected as the benzyl imine) has been similarly alkylated at the ortho position with butyl-lithium. ... 

Photolytic. Synthetic air containing gaseous nitrous acid and toluene exposed to artificial sunlight (Z = 300-450 nm) yielded methyl nitrate, peroxyacetal nitrate, and a nitro aromatic compound tentatively identified as a nitrophenol or nitrocresol (Cox et al., 1980). A n-hexane solution containing toluene and spread as a thin film (4 mm) on cold water (10 °C) was irradiated by a mercury medium pressure lamp. In 3 h, 26% of the toluene photooxidized into benzaldehyde. 

Solid styrene was exposed at — 196°C to ozone, in an attempt to discern whether the behavior of the system is similar to that of olefinic compounds, yielding an ozonide, or to that of aromatic compounds, yielding a 7r-complex. On heating to about — 100°C, an adduct is formed that is stable until about —55 °C, when benzaldehyde and a peroxidic polymer are slowly obtained. The structure of the adduct is probably that of a POZ, based on the similarity of the IR spectrum with the ozone adduct of vinyl chloride described in the preceding paragraph . 

A principally different approach for the indirect electrochemical oxidation of aromatic compounds goes via the formation of hydroxyl radicals from cathodically generated hydrogen peroxide and from reductively formed iron(II) ions. The thus in situ formed Fenton reagent can lead to side-chain as well as nuclear oxidations of aromatic compounds. Side-chain oxidations to form benzaldehydes according to Eqs. (18)—(24) can also be initiated by the redox pairs and Cu instead of... 

Technically interesting are the indirect electrochemical oxidations of benzylic alcohols (Table 11, No. 15-18) benzaldehyde dimethylacetals (Table 11, No. 19) and alkyl aromatic compounds (Table 11, No. 20, 21) It could be proven that benzylic alcohols are oxidizable using tris(2,4-dibromophenyl)amine as mediator not only in acetonitrile in a divided cell but also in methanol in an undivided cell... 

Benzaldehyde, a close structural relative of benzene, is an aromatic compound responsible for the odor of cherries. 

Most of the studies on Botrytis-specific aroma compounds have investigated the aroma composition of wines (Table 6.7). Only a few have focused on what occurs in the grape. On synthetic media, the main odorous compounds produced by B. cinerea are aromatic aldehydes (benzaldehyde, phenylacetaldehyde), and furfural (Kikuchi et al., 1983). Sarrazin et al. (2007a) confirmed the higher concentration of phenylacetaldehyde in noble-rotted grapes. 

Male moths and butterflies have proven to be an especially rich source of interesting natural products. The sex pheromone produced in the wing glands of the lesser waxmoth, Achroia grisella, is composed of n-undecanal and (Zj-ll-octadecenal (98), whereas that of the greater waxmoth also contains n-undecanal (.99) but is dominated by n-nonanal (100). The scent brushes of male noctuid moths produce large amounts of aromatic compounds and terpenes which are believed to function as aphrodisiacs (101). Benzaldehyde, 2-phenyl ethanol, benzyl alcohol, 6-methyl-5-hepten-2-one, pinocarvone, and isobutyric acid have been identified in the secretions of different noctuid species (102), and it appears that these pheromones may possess some chemotaxonomic value. 

The major advantage of the seunpling technique developed, was that some trace chemicals could be trapped tind described for the first time as Black Truffle aroma constituents. In particular, some compounds, important flavor contributors, generally appearing in small concentrations, such as benzaldehyde, propanal, ethyl acetate, anisole or dimethyl disulfide - previously identified in Shiitake mushrooms (9) - could be characterized. This was also the case for three aromatic compounds, toluene, xylene and ethyl benzene, well known as raw vegetable constituents (1 ). In addition, two aliphatic esters, isopropyl and sec-butyl formates, and one cyclic sulfur compound (2-formyl thiophene) previously reported respectively in plums and apples (W) and in coffee and bread products (n) were identified. 

Styrene undergoes many reactions of an unsaturated compound, such as addition, and of an aromatic compound, such as substitution (2,8). It reacts with various oxidizing agents to form styrene oxide, benzaldehyde, benzoic acid, and other oxygenated compounds. It reacts with benzene on an acidic catalyst to form diphenylethane. Further dehydrogenation of styrene to phenjdacetjdene is unfavorable even at the high temperature of 600 C, but a concentration of about 50 ppm of phenylacetylene is usually seen in the commercial styrene product. 

The system consisting of gaseous BFs/EtsSiH has been reported "- to reduce aldehydes and ketones thus benzaldehyde was reduced to toluene in 52% yield. In alkyl carbonyl compounds, aldehydes afford the corresponding alcohol products, whereas ketones, such as undecan-2-one and cyclohexanone, are readily converted to the hydrocarbons in high yields. On reduction with limited amounts of both reagents these alkyl ketones were reduced to the alcohols, indicating the intermediacy of the corresponding borate ester. In the case of aromatic compounds, aryl aldehydes and diaryl and alkyl aryl ketones are reduced to... 

Many types of aromatic substrate are known to undergo a cyclometallation reaction when exposed to alkylpentacar-bonylmanganese complexes under thermal conditions. It is well established that the treatment of ligand appended arenes with alkylmanganesepentacarbonyl complexes can lead to the formation of [C,Y] heterochelates of Mn(CO)4 (Y being a two-electron donor ligand) (Equation 6). For instance, aromatic compounds such as W,W-dimethylbenzyl-amine, alkyl benzyl thioethers, 2-phenylpyridine, acetophenone, benzaldehyde, and diazobenzene can be readily... 

Further cleavage of the chain with double bonds formed after the alcohol elimination explains the formation of some aromatic compounds such as benzene, toluene, styrene, benzaldehyde, etc. Two other common small molecules in the pyrolysate are phenol and the corresponding acid of the side chain substituent. 

Alkyl-substituted benzenes and alkyl-substituted aromatic compounds constitute the starting molecules. Benzaldehydes, benzyl acetates, and to some extent also benzyl alcohols are the main intermediates aromatic carboxylic acids are the desired products. The intermediate benzyl acetates, benzaldehydes, and the corresponding acids can also be formed in stoichiometric reactions with Co(OAc)3 in acetic acid in the absence of oxygen. 

For natural benzyl acetate a 8 C-value of -29.1%o has been found, while -26.5%o was measured for the nature-identical product. The 5 H-value of natural benzyl acetate (-113%o) is quite similar to that of other natural aromatic compounds, while for a nature-identical product a value of -i-352%o has been found [265]. The reasons may be similar to those discussed for synthetic benzaldehyde. 

A methyl substituted aromatic compound such as p-cresol can be best converted to the corresponding aldehyde such as p-hydroxy benzaldehyde by reacting a methanolic alkaline p-cresol in presence of a mixed co-acetate-Mn-acetate catalyst at a pressure of 8-lOkg/cm and temperature of 75-100°C in presence of air and a solvent such as piperidine or an amine (ammonia, triethylamine, etc.) that would yield approximately 80-90% of the aldehyde in about 16-18 hr. 

A variety of other, nonaromatic, aldehydes with 26 have also given the expected esters.Ferrocenecarboxaldehyde has been allowed to react with the anions of both the quinoline and isoquinoline Reissert compound. Benzaldehyde and other aromatic aldehydes have been condensed with the anion of the phthalazine Reissert compound. 

The use of electricity in reactions is clean and, at least in some cases, can produce no waste. Toxic heavy metal ions need not be involved in the reaction. Hazardous or expensive reagents, if needed, can be generated in situ where contact with them will not occur. The actual oxidant is used in catalytic amounts, with its reduced form being reoxidized continuously by the electricity. In this way, 1 mol% of ruthenium(III) chloride can be used in aqueous sodium chloride to oxidize benzyl alcohol to benzaldehyde at 25°C in 80% yield. The benzaldehyde can, in turn, be oxidized to benzoic acid by the same system in 90% yield.289 The actual oxidant is ruthenium tetroxide. Naphthalene can be oxidized to naphthoquinone with 98% selectivity using a small amount of cerium salt in aqueous methanesulfonic acid when the cerium(III) that forms is reoxidized to cerium(IV) electrically.290 Substituted aromatic compounds can be oxidized to the corresponding phenols electrically with a platinum electrode in trifluoroacetic acid, tri-ethylamine, and methylene chloride.291 With ethyl benzoate, the product is a mixture of 44 34 22 o/m/fhhy-... 

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