Low molecular weight carbonyl compound

Zhou X. and Mopper K. (1997) Photochemical production of low-molecular-weight carbonyl compounds in seawater and surface microlayer and their air-sea exchange. Mar. Chem. 56, 201-213. 

Low Molecular Weight Carbonyl Compounds. In the dairy field, a major product made this way is starter distillate. The main component is diaceyl which is a very important aroma compound responsible for the characteristic buttery flavor of fermented dairy products such as sour cream or buttermilk. The dairy industry relies upon fermentation by lactic streptococci for the production of diacetyl in cultured products. Starter distillate is a natural product rich in diacetyl which is produced by distilling such lactic cultures. The key intermediate in the biosynthesis of diacetyl is aL-acetolactic acid which is decarboxylated to form diacetyl (Figure 3). The starting material of the biosynthetic pathway is citrate which is a natural component of milk. 

HPLC is mainly used for the analysis of the derivatives of low molecular weight carbonyl compounds such as formaldehyde [40, 59, 65]. However, formaldehyde is also quantified by a variety of other procedures, including the spectrometric acetyl-acetone method [66] and the chromotropic acid pro-... 

Low molecular weight carbonyl compounds in ETS were collected as their 2,4-DNPH derivatives. 

Vairavamurthy A., Roberts J.M. and Newman L. (1992) Methods for determination of low molecular weight carbonyl compounds in the atmosphere a review. Atmos. Environ., 26A, 1965-1993. 

Liquids obtained by fast pyrolysis of four different woods were analysed. On addition of excess water they separated into water-soluble and water-insoluble fractions. The former which is principally of carbohydrate origin was shown by HPLC analysis to consist of sugars, anhydrosugars and low molecular weight carbonyl compounds. The latter was shown by NMR to be a "pyrolytic lignin". In this way 81% to 92% of the organic content of the liquids has been characterised. 

Before the age of chromatography, the characterization of unknown compounds necessitated the preparation of crystalline derivatives with definite melting points. For this purpose, hydroxylamine and phenylhydrazine are not always ideal reagents, particularly for low molecular weight carbonyl compounds. These derivatives possess rather low melting points or may even be oils at room temperature. The oximes are often very soluble and therefore difficult to purify, and mixtures of stereoisomers may also be formed. With phenylhydrazine, variations in the reaction procedure can lead to different derivatives a-diketones yield mono- and dihydrazones... 

Another example of the resin-capture-release technique which should see widespread applications in the future is the selenium-mediated functionalization of organic compounds. Polymer-supported selenium-derived reagents [34] are very versatile because a rich chemistry around the carbon-selenium bond has been established in solution and the difficulties arising from the odor and the toxicity of low-molecular weight selenium compounds can be avoided. Thus, reagent 26 (X = Cl) was first prepared by Michels, Kato and Heitz [35] and was employed in reactions with carbonyl compounds. This treatment yielded polymer-bound a-seleno intermediates, which were set free back into solution as enones from hydrogen peroxide induced elimination. Recently, new selenium-based functionalized polymers 26 (X = Br)-28 were developed, which have been utilized in syntheses according to Scheme 11 (refer also to Scheme 3) [36],... 

The oxygenated organics comprise compounds such as low molecular weight carbonyls, alcohols, and peroxides. As with the NMHCs and alkyl... 

Polymerization and scission reactions begin and yield high molecular weight cross-linked products and low molecular weight carbonyl and hydroxy compounds carbon dioxide and water are also formed and are present in the volatile products of film formation. 

Highly lipophilic weak acids and bases that have the capacity to remain lipophilic in both their protonated and deprotonated forms can act as protonophores. Such compounds belong to another class of ionophores that are often referred to as mitochondrial uncouplers because of their unique ability to translocate protons across mitochondrial membranes, resulting in the subsequent loss of the mitochondrial proton gradient that is required to drive oxidative phosphorylation. While certain natural products act as mitochondrial uncouplers, most of the protonophores used as pharmacological probes are not natural products but are low-molecular-weight synthetic compounds (e.g., carbonyl cyanide -trifluoromethoxyphenylhydrazone (FCCP)). 

As a result of the above constraints, VOCs that for all practical purposes do not produce organic aerosol in the atmosphere include all alkanes with up to six carbon atoms (from methane to hexane isomers), all alkenes with up to six carbon atoms (from ethene to hexene isomers), benzene and many low-molecular-weight carbonyls, chlorinated compounds, and oxygenated solvents. 

Methyl butanal is a typical carbonyl which has been previously identified in peanuts. Mason et al (15). 2,5-Dimethyl pyrazine is also a typical compound which has been previously reported in peanuts (Mason et al) (16). A decrease in aldehyde and subsequent increase in pyrazine with increased roasting time was demonstrated by these authors. This svpports Mason and Johnson s findings (15, 16). They reported that the low molecular weight carbonyls, particularly aldehydes, were responsible for the harsh green notes present in roasted peanuts while the alkylated pyrazines were responsible for the roasted nutty character of roasted peanuts (3, 16). 

Milic, L Hoffmann, R. Fedorova, M. Simultaneous detection of low and high molecular weight carbonylated compounds derived from lipid peroxidation by electrospray ionization-tandem mass spectrometry. Ana/. Chem. 2013, 85,156-162. 

Cyclic Peroxides. CycHc diperoxides (4) and triperoxides (5) are soHds and the low molecular weight compounds are shock-sensitive and explosive (151). The melting points of some characteristic compounds of this type are given in Table 5. They can be reduced to carbonyl compounds and alcohols with zinc and alkaH, zinc and acetic acid, aluminum amalgam, Grignard reagents, and warm acidified iodides (44,122). They are more difficult to analyze by titration with acidified iodides than the acycHc peroxides and have been sucessfuUy analyzed by gas chromatography (112). 

Low -molecular-weight ozonides are explosive and are theretore not isolated. Instead, the ozonide is immediately treated with a reducing agent such as zinc metal in acetic acid to convert it to carbonyl compounds. The net result of the ozonolysis/reduction sequence is that the C=C bond is cleaved and oxygen becomes doubly bonded to each of the original alkene carbons. If an alkene with a letrasubstituted double bond is ozonized, two ketone fragments result if an alkene with a trisubstituted double bond is ozonized, one ketone and one aldehyde result and so on. 

Polymers obtained have a low molecular weight and contain carbonyl end groups, even in the case of initial systems with a 1 1 mole ratio of diamine to dicarbonyl compound. 

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