Synthesis of Alkyl Chlorides

The synthesis of alkyl chlorides by adding HCl to an alkene illustrates the mechanistic features of the reaction, but alkenes react very slowly with HCl. This difficulty can be avoided by changing the reactions conditions. When an alkene is tteated with trimethylsilyl chloride, (CH3)3CC1, and water, HCl rapidly adds across the double bond giving a high yield of product. The reaction follows Mar- 

Markovnikov s rule is explained by the mechanism of the reaction. Consider the reaction ofpropene MECHANISTIC BAS IS HBr. The n electrons in propene act as a Lewis base, and react with a proton, which is an elec- 

In the second step of the addition reaction, the scc-butyl carbocation, which has a vacant 2p orbital, acts as a Lewis acid. It accepts an electron pair from the nucleophilic bromide ion. This mechanism accounts for the product predicted by Markovnikov s rule. 

The reaction of propene with HBr is shown below. In this case, two different carbocations are possible If the hydrogen atom had bonded to C-2, a primary, -propyl carbocation would have formed if the hydrogen bonds to C-3 of propene, a secondary, isopropyl carbocation forms. Since a secondary carbocation is more stable than a primary carbocation, only 2-bromoproane forms. 

The isopropyl carbocation has the positive charge on a secondary carbon atom. The -propyl carbocation has the positive charge on a primary carbon atom. The isopropyl carbocation forms, rather than the -propyl cation, because the larger number of alkyl groups attached to a positively charged carbon atom help to stabilize the charge. 

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Table I. Synthesis of Alkyl Chlorides form Carbon Tetrachloride, a Phosphinated Soluble Polymer and an Alcohol or Thiol...

A new synthesis of alkyl chlorides consists of the interaction of 2-alkoxy-3-ethylbenzoxazolium salts (54a), formed in situ from alcohols and a 2-chloro-3-ethylbenzoxazolium salt (Scheme 32), with tetraethylammonium chloride. This... 

Alkyl fluorides are valuable compounds for study as well as convenient precursors for the construction of complex organic architectures with a high degree of functionalization. A range of routes have been devised for the synthesis of these compounds, and a number of reviews on the synthesis of alkyl fluorides have appeared [1-6], One of the most direct routes to the preparation of an alkyl fluoride would be the deoxyfluorination of alcohols. Fundamentally, this would be analogous to a fluorine version of the Appel reaction, and while the Appel reaction is one of the most successful approaches to the synthesis of alkyl chlorides and bromides [7], it has been challenging to extend the chanistry to the preparation of aUcyl fluorides [6],... 

PE oligomers. These oligomers are used as homogeneous polymeric reagents for the synthesis of alkyl chlorides from alcohols in CCl4-toluene at 90... 

A considerable amount of hydrobromic acid is consumed in the manufacture of inorganic bromides, as well as in the synthesis of alkyl bromides from alcohols. The acid can also be used to hydrobrominate olefins (qv). The addition can take place by an ionic mechanism, usually in a polar solvent, according to Markownikoff s rule to yield a secondary alkyl bromide. Under the influence of a free-radical catalyst, in aprotic, nonpolar solvents, dry hydrogen bromide reacts with an a-olefin to produce a primary alkyl bromide as the predominant product. Primary alkyl bromides are useful in synthesizing other compounds and are 40—60 times as reactive as the corresponding chlorides (6). 

Yields of chlorides are good to excellent for primary and secondary alcohols, but a competing olefin-forming elimination process renders the method of limited value for preparing tertiary chlorides.12 An adaptation of the procedure using carbon tetrabromide allows the synthesis of alkyl bromides. Some examples are the preparation of rt-C5H11Br (97%) and C H6CH2Br (96%).12 Farncsyl bromide has been prepared in 90% yield from fame sol.23... 

A viable iron carbonyl-mediated reduction process converts acid chlorides and bromoalkanes into aldehydes [3, 6]. Yields are high, with the exception of nitro-benzoyl chloride, and the procedure is generally applicable for the synthesis of alkyl, aryl and a,(i-unsaturated aldehydes from the acid chlorides. The reduction proceeds via the initial formation of the acyl iron complex, followed by hydride transfer and extrusion of the aldehyde (cf. Chapter 8). 

Grove s synthesis org chem Production of alkyl chlorides by passing hydrochloric acid into an alcohol In the presence of anhydrous zinc chloride. grovz sin-th3S3s ) GR-S rubber org chem Former designation for general-purpose synthetic rubbers formed by copolymerization of emulsions of styrene and butadiene used in tires and other rubber products previously also known as Buna-S, currently known as SBR (styrene-butadiene rubber). je ar es. rab ar)... 

An important reaction for synthesis of alkyl and dialkylethanoic acids (RX and R X are primary or secondary alkyl halides) dicarboxylic acids (RX = haloester) unsaturated acids (RX = an unsaturated halide, best for allylic halides) /3-keto acids (R = acyl chloride) (see Sections 18-8C and 18-8D). 

It follows from all the above-mentioned facts that the direct synthesis of methyl-, ethyl and phenylchlorosilanes is a complex heterophase process which depends on many factors and forms a compex reactive mixture. For example, in the direct synthesis of methylchlorosilanes there are about 130 compounds found and characterised. This does not mean, however, that in this or other definite synthesis all the 130 products are formed. The composition of the mixtures formed and the transformation degree of alkyl-chlorides and chlorobenzene in the synthesis of methyl-, ethyl and phenylchlorosilanes depend on the synthesis conditions, the type of the reactor used and many other factors. In spire of the complexity of the process and the variety of its products, the reaction of direct synthesis can nevertheless be directed (towards a preferential formation of a main product), changing the conditions for the preparation of contact mass, introducing various promoters into contact mass and changing the reaction conditions. 

The Finkelstein procedure169 exploits the solubility differences between halide salts (e.g. Nal and NaCl in acetone170) to effect the conversion of alkyl chlorides to alkyl iodides. Ferric chloride has been used as catalyst in Finkelstein reaction of tertiary alkyl and benzyl chlorides and sodium iodide in nonpolar solvents171. Cu(I) iodide, combined with potassium iodide in HMPA, is used for the synthesis of gem-diiodoolefins from the corresponding gem-dibromides172. 

Preparation of Chiral Sulfinates. Optically active sulfinates can be prepared by reaction of a symmetrical sulfite with t-Butylmagnesium Chloride in the presence of an optically active amino alcohol. The best enantioselectivity has been observed using quinine as the optically active amine (eq 2)3 An alternative approach to this new enantioselective asymmetric synthesis of alkyl t-butylsulfinates would be reaction of a racemic sulfinate with r-butylmagnesium chloride complexed by optically active alkaloids (eq 3). In this case, kinetic resolution of the racemic sulfinate leads to an optically active sulfinate and an optically active sulfoxide. 

CLAY KINNEAR PERREN Phosphonyl Chtoride Synthesis Synthesis of alkyl phosphonyl chlondes from alkyl chlorides or from ethers with PCI3 AICI3... 

The condensation of a, dicarbonyl compounds (49) with aj3-diamino compounds (50), which proceeds through the dihydropyrazine (51), has been much used for the synthesis of alkyl- and arylpyrazines (52). These reactions are usually carried out in methanol, ethanol, or ether in the presence of sodium or potassium hydroxide. The dihydropyrazines may be isolated, or oxidized directly to the pyrazine. Dehydrogenating agents that have been employed include oxygen in aqueous alkali (329), air in the presence of potassium hydroxide (330), sodium amylate in amyl alcohol (330a), alcoholic ferric chloride (24), and copper chromite catalyst at 300° (331) (see also Section 1). Pyrazines prepared by this method and modifications described below are listed in Table II.8 (2, 6, 24, 60, 80,195, 329-382) and some additional data are provided in Sections VI. 1 A, VlII.lA(l), and IX.4A(1). 

The success of FCC encouraged applications of the fluidized catalyst reactor to other catalytic reactions. Successful applications can be found in fluid catalytic reforming, production of alkyl chloride by oxychlorina-tion, production of phthalic anhydride, acrylonitrile synthesis by ammox-idation, and production of maleic anhydride. 

A general method fen the synthesis of alkyl iodides is the reaction of tosylates or methanesulfonates with sodium iodide in acetone or magnesium iodide in diethyl ether (equation 30). The reaction is not always a clean Sn2 process. Stereoselectively deuterated neopentyl tosylate, for example, gives with Nal in HMPA only low yields (34%) of the racemic iodide (equation 31). This is in contrast to analogous reactions with bromide and chloride (see Sections 1.7.3.2 and 1.7.2.2), where better yields with complete inversion are observed. 

In contrast to thioacyl chlorides, thiophosgene, CSCh, is readily accessible and conveniently handled making it an important reagent in the synthesis of thiocarbamoyl chlorides (15 ClCSNRa), 0-alkyl thiourethanes (ROCSNR 2), and thioureas (R2NCSNR2) (c/. Volume 6, Chapter 2.8). ... 

Organomercurials can also be used for the synthesis of alkyl complexes. Organomercurials have stable alkyl-mercury bonds, and the alkyl groups can be transferred to transition metal complexes (alkylation of the transition metal complexes). Thus diphenylmercury reacts with one equivalent of dichloroplat-inum complex to produce phenylmercuric chloride and monosubstituted platinum complex in good yield 73). 

Alkylsulphamic acids have been used as starting materials for the synthesis of alkyl sulphamoyl chlorides with a variety of chlorinating agents (equation 82)271-274 Kloeck... 

In general, the ease of synthesis of alkyl halides from olefins is dependent on the molecular weights of the hydrocarbons and the particular hydrogen halide. Thus, as was explained earlier in this chapter, the reaction becomes more difficult in passing from iodides through bromides to chlorides. Likewise, olefins containing several carbon atoms react much more readily than those of a lower order. 

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