Survey of reactions

The major reactions carried out by hydroxyl and nitrate radicals may conveniently be represented for a primary alkane RH or a secondary alkane RjCH. In both, hydrogen abstraction is the initiating reaction. 

The concentration of NO determines the relative importance of reaction 3, and the formation of NO2 is particularly significant since this is readily photolyzed to produce 0( P) that reacts with oxygen to produce ozone. This alkane-NO reaction may produce O3 at the troposphere-stratosphere interface  

This is the main reaction for the formation of ozone although, under equilibrium conditions, the concentrations of NO2, NO, and O3 are interdependent and no net synthesis of O3 occurs. When, however, the equilibrium is disturbed and NO is removed by reactions with alkylperoxy radicals (reactions 1+2+3), synthesis of O3 may take place. 

The extent to which this occurs depends on a number of issues (Finlayson-Pitts and Pitts 1997), including the reactivity of the hydrocarbon that is itself a function of many factors. It has been proposed that the possibility of ozone formation is best described by a reactivity index of incremental hydrocarbon reactivity (Carter and Atkinson 1987, 1989) that combines the rate of formation of O3 with that of the reduction in the concentration of NO. The method has been applied, for example, to oxygenate additives to automobile fuel (Japar et al. 1991), while both anthropogenic compounds and naturally occurring hydrocarbons may be reactive. 

Clearly, whether or not ozone is formed depends also on the rate at which, for example, unsaturated hydrocarbons react with it. Rates of reactions of ozone with alkanes are, as noted above, much slower than for reaction with OH radicals, and reactions with ozone are of the greatest significance with unsaturated aliphatic compounds. The pathways plausibly follow those involved in chemical ozonization (Hudlicky 1990). 

The known CO insertion and decarbonylation reactions are surveyed in this section. Kinetic and stereochemical results already discussed in Sections II-IV have been given a cursory mention for the sake of completeness. Not comprehensively covered are processes which likely proceed via 

CO insertion (as inferred from the nature of products), but in which the actual insertion or decarbonylation step has received at most peripheral attention. This particularly applies to industrial carbonylation processes such as hydroformylation. The interested reader is referred to several excellent articles on these subjects (30, 32, 62, 117, 198a, 203a, 228). 

Reactions of metal carbonyls with alkyllithium reagents to give the corresponding acyls, e.g., conversion of W(CO)g to Li[PhCOW(CO)5] with LiPh (90), undoubtedly involve attack of LiR upon coordinated CO. Another carbanion-like interaction with a bonded CO is thought to be responsible for the formation of 

No CO insertion or decarbonylation studies have been reported for these elements. However, the recent preparation of several stable alkyls (243) may provide some impetus for such investigations.  

Attempts at the carbonylation of CpCr(NO)2Me in hexane or THF at reflux resulted only in recovery of the nitrosylalkyl (105). A recent report of the reaction between CpCr(CO)3Me and L [L = PPhj, P(p-CjH40Me)3, and PMejPh] to yield trawi-CpCr(CO)2L(COMe) furnishes the first example of insertion of CO into Cr—C bonds (19b). 

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Processes with gaseous reactants are excluded here. Due to the large compressibility of gases an increase of pressure (up to 1 kbar) leads essentially only to an increase of gas concentration, and hence to an acceleration of bimolecular processes in which gases are involved as reactants. The effect of pressure on a chemical reaction in compressed solution is largely determined by the volume of reaction (AV) and the volume of activation (AV ). It is not the purpose of this chapter to provide a complete survey of reactions of dienes and polyenes which have been investigated at elevated pressures. There are many excellent monographs (e.g. References 1-4) and reviews (e.g. References 5-16) on this topic which cover the literature up to early 1990. After a short introduction into the basic concepts necessary to understand pressure effects on chemical processes in compressed solutions, our major objective is to review the literature of the past ten years. 

F. J. Dinan and J. F. Bieron, A Survey of Reactions of Thionyl Chloride, Sufuryl Chloride and Sulfur Chlorides, Occidental Chemical Corp., Niagara Falls, N.Y., 1990. 

The survey of reactions used to prepare small-molecule APIs [9] highlighted reactions warranting research to identify greener options for the process chemist, and a subsequent paper by members of the ACS Roundtable substantially expanded this perspective [12]. The following subsections focus on three chemical transformation areas requiring future development, but the reader is referred to the Roundtable reference for a more extended discussion. 

Coordinated CS2 groups can react via dimerization and abstraction of CS2, as can be seen in a survey of reactions of a rhodium(I) phosphine complex with CS2 (Scheme 1). The dimerization can be throught to proceed through a nucleophilic attack on the carbon atom of CS2 via an end-on intermediate of the heteroallene fragment.1011... 

Survey of Reactions between Electrophiles and Enolates and the Issue of Ambidoselectivity... 

Driving Force of Aldol Additions and Survey of Reaction Products... 

TABLE 6. Literature survey of reactions of alkynyliodonium salts with enolates... 

The scope of this review is a detailed survey of reactions proceeding through vinyl cations and an attempt of a systematic definition of the properties of these intermediates with reference to those of saturated carbonium ions. Although attention will be particularly devoted to linear cations, bridged unsaturated species will be considered as alternative structures of vinyl cations rather than as a distinct type of reactive intermediates. The 77--complex terminology (Dewar, 1949) widely abused in the past decades to indicate especially cyclic cations and recently reassessed by Banthorpe (1970) will be generally avoided. The most recent Btudies not covered by published reviews on the subject (Rappoport, 1969 Richey and Richey, 1970 Richey, 1970 Hanack, 1970) are discussed in greater detail than others and data are collected in pertinent Tables. 

The diols (97) from asymmetric dil droxylation are easily converted to cyclic sii e esters (98) and thence to cyclic sulfate esters (99).This two-step process, reaction of the diol (97) with thionyl chloride followed by ruthenium tetroxide catalyzed oxidation, can be done in one pot if desired and transforms the relatively unreactive diol into an epoxide mimic, ue. the 1,2-cyclic sulfate (99), which is an excellent electrophile. A survey of reactions shows that cyclic sulfates can be opened by hydride, azide, fluoride, thiocyanide, carboxylate and nitrate ions. Benzylmagnesium chloride and thie anion of dimethyl malonate can also be used to open the cyclic sulfates. Opening by a nucleophile leads to formation of an intermediate 3-sidfate aiuon (100) which is easily hydrolyzed to a -hydroxy compound (101). Conditions for cat ytic acid hydrolysis have been developed that allow for selective removal of the sulfate ester in the presence of other acid sensitive groups such as acetals, ketals and silyl ethers. 

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