Oxygen-sensitive compounds

Heteroatom-containing derivatives of pentalene and azulene are 8- and 10-jr-electron systems, respectively, and have been extensively studied by Hafner and co-workers.301-304 A few examples are presented in Schemes 30, 47, and 86. Electron-rich azapentalenes 247—249305 306 and various aza-azu-lenes 250—252300-302 have intense colors and are stable but oxygen-sensitive compounds. Azulenes with nitrogen heteroatoms placed in positions with high electron density, such as position 5, or positions 5 and 7, present a hypsochromic effect, while a heteroatom in position 6, with low electron density, exerts a bathochromic effect. When both types of positions are substituted by heteroatoms, their effect is canceled out.307 The bond lengths in 252 (Scheme 86), as determined by X-ray, indicate delocalization as in 252a and 252b.308 309... 

In order to reduce this effect, the samples should be protected from sunlight by wrapping the sample bottles in appropriate material. When dealing with oxygen sensitive compounds, the reactions should be performed under nitrogen or other inert gas atmosphere. 

One of the arguments for the use of (3-cyclodextrin in food is that it can complex deleterious hydrophobic compounds like cholesterol and caffeine whose concentrations may then be lowered or eliminated (Oakenfull and Sidhu, 1992 Hedges et al., 1993). By the same mechanism, (3-cyclodextrin can emulsify water-triglyceride mixtures (Shimada et al., 1992), protect light-, heat-, and oxygen-sensitive compounds, eliminate undesirable flavors and hazes, and stabilize desirable ones (Miyawaki and Konno, 1982). 

In order to measure absorptions of very different intensities with a single solution, or the concentration dependence of the absorption of an oxygen-sensitive compound. 

Cyclodextrin inclusion compounds have found application in pharmacology, the food industry, and cosmetics. Typical examples are the solubilization of insulin and steroids, the removal of cholesterol from egg yolk, and the conservation of basis notes in perfumes by slow release rates of rose oil and similar ingredients. Chemical stabilization of oxygen-sensitive compounds, e.g., the sulfides of onions and garlic flavor, and of vitamins is also achieved by cyclodexteins. 

The first step is to solvent-extract the total additives from the polymer in high yield and with minimnm contamination by low molecnlar polymer. Extracts should be used for analysis withont delay as they may contain light or oxygen sensitive compounds. When delay is nnavoidable, storage in actinic glassware nnder nitrogen in a refrigerator minimises the risk of decomposition. 

A series of novel silicon-, germanium-, or tin-functionalized cumulenes (218) has been prepared by insertion of alkadienylidenecarbenes (217) into the appropriate metal hydrides. The cumulenes are isolable but moderately oxygen-sensitive compounds that rearrange or polymerize on standing at room temperature. An improved synthesis of 1,2,3-butatrienyl ethers has been developed. ... 

The formation of inclusion complexes can stabilize labile compounds and provide protection for light- or oxygen-sensitive compounds. Inclusion complexes can also be used to control the release, stability, solubility, and utilization of biologically active compounds such as drugs, vitamins, flavors, odors, insecticides, herbicides, and so forth. The cyclomaltodextrins can also be used to mask, alter, and/or eliminate undesirable flavors or odors, and they can be used to increase the water solubility of compounds that otherwise have low solubility [16]. 

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