REACTIONS WITH OXYGEN COMPOUNDS

These reactions usually proceed more slowly than the reactions of the corresponding alcohols or phenols with boron halides. In some cases, where direct reaction is too slow, the lead or mercury derivatives of thiols are used. Attempts to use the reactions of thiols with diboron trisulfide to prepare trialkylthioboranes have usually been unsuccessful, although analogous reactions with oxygen compounds are commonly used to prepare trialkoxyboranes. Formation of B-S bonds... 

REACTIONS WITH OXYGEN COMPOUNDS 10.3.1 Alcohols, phenols and their derivatives... 

Reactions with Oxygenated Compounds. A recent study (14,44) has reported on the reactions of CF3+, CF2CI, 0012 , and C2F with a series of organic molecules containing a carbonyl functional group. These Ions undergo four-center reactions with such compounds, which In the case of aldehydes and ketones lead to a product In which the carbony oxygen of the reactai t compound has been replaced by a F (or Cl ). For Instance, CF3 reacts with acetone as follows ... 

The reactivity of the transition metals towards other elements varies widely. In theory, the tendency to form other compounds both in the solid state (for example reactions to form cations) should diminish along the series in practice, resistance to reaction with oxygen (due to formation of a surface layer of oxide) causes chromium (for example) to behave abnormally hence regularities in reactivity are not easily observed. It is now appropriate to consider the individual transition metals. 

The standard reduction potential of Cr " (Table 2) shows that this ion is a strong reducing agent, and Cr(II) compounds have been used as reagents in analytical chemistry procedures (26). The reduction potential also explains why Cr(II) compounds are unstable in aqueous solutions. In the presence of air, the oxidation to Cr(III) occurs by reaction with oxygen. However, Cr(II) also reacts with water in deoxygenated solutions, depending on acidity and the anion present, to produce H2 and Cr(III) (27,28). 

B. Ranby and J. F. Rabek (eds.) Singlet Oxygen Reactions with Organic Compounds and Polymers, Wiley, Chichester, 1978, 331 pp. 

Sometimes, knowing only the magnitude of the equilibrium constant, it is possible to decide on the feasibility of a reaction. Consider, for example, a possible method for fixing atmospheric nitrogen—converting it to a compound—by reaction with oxygen ... 

The HQ reaction with oxygen proceeds through several steps, and the precise reaction path is pressure-dependent. The first step is the formation of benzoquinone is shown in the following section. Further reactions result in the formation of low MW alcohols, ketones, andother compounds. 

Sulfur compounds " are better nucleophiles than their oxygen analogs (p. 439), so in most cases these reactions take place faster and more smoothly than the corresponding reactions with oxygen nucleophiles. There is evidence that some of these reactions take place by SET mechanisms. ... 

Oxidation by reaction with oxygen in the air is a major use of paraffins. Paraffins are converted to more reactive compounds called olehns by cracking under pressure at high temperature. 

Lenoir, D. (2006) Selective Oxidation of Organic Compounds - Sustainable Catalytic Reactions with Oxygen and without Transition Metals Angewandte Chemie International Edition, 45, 3206-3210. 

The durability of the antioxidant can be affected by a number of factors, the most important being the amount present in the compound. The process of vulcanisation can result in the loss of migratory or volatile antioxidants. Over long periods of service, the antioxidant will decrease in concentration at ambient temperatures due to reaction with oxygen. Loss by volatility is usually only a problem with antioxidants such as the mono-phenolics. 

However, the initial absence of unstable groups is no guarantee for long-term stability of the compound. For example, some aldehydes and ethers are easily converted to peroxides by reaction with oxygen from air [35,37,38]. Organic peroxides represent a class of unstable materials while monomers represent a class of substances that can self-react by polymerization if not properly inhibited and if the temperature is not properly maintained. Runaway reactions can result in both of these examples. 

Exposure of alkyllithium or aryllithium compounds to the atmosphere may cause degradation due to reaction with oxygen (equation 1) or air moisture (equation 2). Certain organolithium compounds are unstable at room temperature in the neat form, and require dilution even then they should best be stored at low temperature. The instability may be the result of reactions such as the eliminations depicted in equations 3 and 4, taking place as the temperature rises . 

The photochemistry of thiocarbonyl compounds has been extensively studied over the past three decades, and a variety of photochemical reactions are developed [1-8]. One of the earliest photochemical reactions of thiones is the reaction with oxygen [9]. Schonberg and Stephenson reported a detailed study of the photodimerization of thiophosgene and the wavelength-dependent pho-... 

Compounds 16 and 19 each deliver the expected six alcohols after reduction of the primarily formed hydroperoxide mixtures as a result of an oxygen attack on the trisubstituted A1 double bonds of these molecules. The ratio of tertiary/secondary hydroperoxides (or alcohols) is about 44 56, as has also been found with 1-methylcyclohexene (30)13S while open-chain olefins such as trimethylethylene (S3), 1,1-dimethyl-2-ethylethylene (id), 2,6-dimethyl-2-octene (39), myrcene (42), / -citronellol (45), linalool (48), and l,l-dimethyl-2-benzylethylene (51) give ratios of tertiary/secondary hydroperoxides between 54 46 and 60 40.104-1 7 7 1 79 The slight deviations from 1 1 ratios in all these cases are probably due to stereochemical rather than electronic effects exerted by the olefins on the reaction with oxygen. 

Shifting and rearrangement of bonds within a molecule due to reaction with oxygen can result in the formation of compounds which impart color to fuel. These compounds often have some degree of aromatic functionality. The color imparted to the fuel is typically amber to brown. Some distillate fuels turn deep red in appearance while others appear pale green. 

Methyl benzoate, anisole, and diphenyl ether each give sandwich compounds with chromium vapor, although in rather low yield (32, 55, 110). Chromium appears to attack alkyl ethers and this deoxygenation probably competes with complexation with the aromatic oxygen compounds. No simple product has been isolated from chromium atoms and aniline, but bis(7V,7V-dimethylaniline)chromium has been prepared (32). The behavior of molybdenum and tungsten vapors closely resembles that of chromium in reactions with oxygen- and nitrogen-substituted arenes (113). 

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