Alkyls and aiyls

Monochlorophenols. Chlorination of phenol [108-95-2] between 50 and 120°C gives a ortho ratio of 1.65. To improve the selectivity in the paia position, it is possible to use dialkyl sulfides, diaiyl sulfides (12), oi alkyl and aiyl sulfides combined. Sulfides are active only at low tempeiatuies (<50 C), because at high tempeiatuies the active species decomposes into sulfui and chlorine. 

Alcohols and phenols eonsist of two parts, an alkyl/aiyl group and a hydrojQTl group. The properties of alcohols and phenols are ehiefly due to the hydrojQTl group. The nature of alkyl and aiyl groups simply modify these properties. 

Alkyl and aiyl arenediazoates ( diazoethers ) are generally unstable and even explosive eompoimds. They are produeed by interaetion of aleohols with (explosive) bis(arenediazo) oxides, or of p-bloeked phenols with diazonium salts. The thio analogues are similar. Individually indexed eompounds are ... 

Fig. 83 Proton chemical shifts for organic compounds in dilute solutions of CC14 or CDC13. R and Ar stand for alkyl and aiyl groups.

The process of the direct synthesis of organochlorosilanes is heterophase. However, it differs from many other heterophase processes in that solid silicon mixed with the catalyst is one of the parent components and is thus constantly spent during synthesis. It means that, as the reaction products form, the amount of the solid phase continually decreases. At the same time, the ratio of silicon and catalyst in contact mass also changes, until silicon is spent completely, which naturally impairs the conditions of the reaction. That is why there are several requirements to the construction of contact apparatuses for the effective direct synthesis of alkyl- and aiyl-chlorosilanes. So, the contact apparatus should provide for ... 

Silylenes are electron deficient, in most cases transient species. Only a few stable derivatives are known so far [1]. For syntheses employing silylenes, they have to be generated in situ. For this purpose alkyl- and aiyl-silylenes can be prepared, e.g., from 7-silanorbomadiene compounds by thermal or photo-... 

The electrochemistry of Ge and Si porphyrins with o-bonded alkyl and aiyl groups has been investigated by Kadish and Guilard The reactions are complicated and must be carried out both in the dark and in the strict absence of O2. An insertion of O2 into the Ge-carbon bond of Ge(Por)(R)2 has been postulated but later studies show that these reactions are actually more complicated than initially suggested The reduction of Ge(Por)(R)2 and Si(Por)(R)2 occurs in either one or two single electron transfer steps. E1/2 values of —1.45 V and —1.48 V are obtained for the first reduction of Ge(OEP)(CH3)2 and Si(OEP)(CH3)2 in PhCN and no second reduction is observed in this solvent In contrast, Ge(TPP)(CeHs)2 is reduced in two steps which occur at - 1.10 and - 1.65 V in PhCN. Similar values of - 1.17 V and -1.72 vs. SCE are measured for the reduction of Ge(TPP)(CH2CsH5)2. First and second reduction poten-... 

Kinetic Resolution of Alcohols. Primary alcohols may be resolved with moderate to good selectivities by Pseudomonas sp. lipase (PSL) using vinyl acetate [186] or acetic anhydride as the acyl dmior (Scheme 3.9). Whereas the selectivities achieved were moderate with alkyl and aiyl substituents, substrate modification via introduction of a bulky sulfur atom in helped considerably. In this way, chiral isoprenoid synthons having a Cs-backlxMie were obtained in >98% enantiomeric excess. 

Some patents and publications suggest flame retardancy advantages for the higher oligomers (132,133). A systematic study of the oligomers and polymers made from alkyl and aiyl dichlorophosphates and dihydric phenols showed that their flame retardancy (as expressed by oxygen index) is a function of phosphorus content and of thermal stability (134). 

In combination with a Burkholderia cepacia lipase (PS-D I) for the kinetic resolution, various primary alcohols were converted into the corresponding enan-tiomerically pure esters in high yields (70-87%) and ee values ranging from 70% to 99% (17). The protocol was found applicable to both alkyl- and aiyl-substituted primary alcohols. 

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