Chloroalkanes conversion

Use thionyl chloride, SOC12, for the alcohol to chloroalkane conversion. Using thionyl chloride with secondary alcohols shifts the mechanism from SN1 to SN2 and, therefore, removes carbocation formation from the process. No carbocation, less risk of rearrangement. 

Pyrolysis. Vinyl chloride is more stable than saturated chloroalkanes to thermal pyrolysis, which is why nearly all vinyl chloride made commercially comes from thermal dehydrochlorination of EDC. When vinyl chloride is heated to 450°C, only small amounts of acetylene form. Litde conversion of vinyl chloride occurs, even at 525—575°C, and the main products are chloroprene [126-99-8] and acetylene. The presence of HCl lowers the amount of chloroprene formed. 

No systematic studies of a number of compoimds have yet appeared to discover correlations suggestive of mechanism. This paper presents the fractional conversions and reaction rates measured under reference conditions (50 mg contaminants/m ) in air at 7% relative humidity (1000 mg/m H2O), for 18 compounds including representatives of the important contaminant classes of alcohols, ethers, alkanes, chloroethenes, chloroalkanes, and aromatics. Plots of these conversions and rates vs. hydroxyl radical and chlorine radical rate constants, vs. the reactant coverage (dark conditions), and vs. the product of rate constant times coverage are constructed to discern which of the proposed mechanistic suggestions appear dominant. 

The simplest C-C bond formation reaction is the nucleophilic displacement of a halide ion from a haloalkane by the cyanide ion. This was one of the first reactions for which the kinetics under phase-transfer catalysed conditions was investigated and patented [l-3] and is widely used [e.g. 4-12], The reaction has been the subject of a large number of patents and it is frequently used as a standard reaction for the assessment of the effectiveness of the catalyst. Although the majority of reactions are conducted under liquiddiquid two-phase conditions, it has also been conducted under solidrliquid two-phase conditions [13] but, as with many other reactions carried out under such conditions, a trace of water is necessary for optimum success. Triphase catalysis [14] and use of the preformed quaternary ammonium cyanide [e.g. 15] have also been applied to the conversion of haloalkanes into the corresponding nitriles. Polymer-bound chloroalkanes react with sodium cyanide and cyanoalkanes under phase-transfer catalytic conditions [16],... 

Selected examples of the conversion of alcohols into chloroalkanes... 

In the presence of tin(IV) chloride or antimony(V) chloride, bromine trifluoride also effects the substitution of chlorine by fluorine in mono- and polychloroalkanes.112 A 30 to 50% excess of bromine trifluoride is necessary for 90-95 % conversion of the starting chloroalkanes. In some cases the substitution of primary chlorine atoms induces hydride shifts. 

Chloroalkanes.1 The conversion of primary alcohols to 1-chloroalkanes with aqueous hydrochloric acid is not useful because of mediocre yields (30-60%). The rate and yield of this reaction are improved considerably by use of a surfactant such as cetyltrimethylammonium bromide or cetylpyridinium bromide. 

The phenylethanolamine (444) reacted with the nitramine (445) in xylene to give the guanidine (446), Conversion to the chloroalkane followed by treatment with sodium or direct exposure of (446) to concentrated sulphuric acid gave imafen (447) Scheme 5.105.). Resolution with (+)-tartaric acid revealed that deximafen is the more active isomer [594-597], The drugs have both been used as antidepressants [598],... 

The major products are secondary alkanesulfonyl chlorides with a statistical distribution of sulfonic groups on the internal carbon atoms of the linear chain. In contrast, the presence of the SO2CI group at the end of the chain is unlikely because of the much lower stability of primary radicals RCHJ. Besides, di- and polysulfochlorides, as well as chloroalkanes are also formed as by-products and a large amount of HCl is generated. Selectivity reaches 85-90% with excess SO2 and low paraffin conversion [32,37]. The quantum yield of a photochemical reaction at a wavelength X is given by ... 

This reaction scheme was first observed by Kharasch and Read [40], but no industrial application has yet been developed because of poor yield and selectivity with linear parafQns. The yield of alkyl chlorides may be higher than that of sulfochlorides [23]. However, some recent works have shown that in the presence of an adequate catalyst (e.g., pyridine) for rather low conversion rates (e.g., 15%), sulfuryl chloride can lead to acceptable RSOjCl/RCl ratio (about 1 in pure phase and higher in benzene solvent) and the quasi absence of di- and polysubstituled compounds [39-45]. Without doubt, the main drawback of the process is still the large amount of alkyl chlorides produced it is then necessary to consider the possible recovery and transformation of the chloroalkane mixtures through quatemization into alkyltrimethylammonium chlorides (cationic surfactants) [46,47] ... 

Dichloromethane has a UV cutoff of 233 nm and is effectively used for compounds with chromophores with > 250 nm. However, since it is used at such low levels in NP work, absoifoance is rarely an issue. Dichloromethane (and chloroform) is unstable and degrades through a free-radical process. Amylene and cyclohexene are commonly used chloroalkane preservatives. Although commonly used as a low-volume mobile phase component in NP separations, dichloromethane has found only limited use in RP work because of its low water solubility. Conversely, solubility with alkanes and good sample-solubilizing characteristics make dichloromethane a very useful component in NP mobile phases. 

The most widely used reagent for the conversion of primary and secondary alcohols to chloroalkanes is thionyl chloride, SOCI2. Yields are high, and rearrangements are seldom observed. The by-products of this conversion are HCl and SO2. 

The mechanism for the reaction of thionyl chloride with a carboxylic acid to form an acid chloride is similar to that presented in Section 10.5C for the conversion of an alcohol to a chloroalkane and involves initial chlorosulfite formation, followed by nucleophilic attack of chloride ion on the carbonyl carbon to give a tetrahedral carbonyl addition intermediate, which decomposes to give the acid chloride, SO2, and chloride ion. 

This synthesis can also be accomplished by conversion of the chloroalkane to a Grignard reagent followed by carbonation and hydrolysis in aqueous add. 

The advantages of the partial chlorination of alcohols (60-95% conversion) with HCl and completion of the chlorination by a catalytic phosgenation and subsequent decarboxylation of the resulting chloroformates have been combined in a two-stage process [974, 982]. Only small amounts of dialkyl ethers, alkenes, isomeric chloroalkanes, or dialkyl carbonates are claimed to be formed as side products. 

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