Radicals chlorination

Write equations for the initiation and propagation steps for the formation of dichloromethane by free radical chlorination of chloromethane... 

In both the following exercises assume that all the methylene groups in the alkane are equally reactive as sites of free radical chlorination... 

Cyclopropyl chlonde has been prepared by the free radical chlorination of cyclopropane Wnte a stepwise mechanism for this reaction... 

Addition to double bonds is not the only kind of reaction that converts an achiral molecule to a chiral one Other possibilities include substitution reactions such as the formation of 2 chlorobutane by free radical chlorination of butane Here again the prod uct IS chiral but racemic... 

Benzyl Chloride. Benzyl chloride is manufactured by high temperature free-radical chlorination of toluene. The yield of benzyl chloride is maximized by use of excess toluene in the feed. More than half of the benzyl chloride produced is converted by butyl benzyl phthalate by reaction with monosodium butyl phthalate. The remainder is hydrolyzed to benzyl alcohol, which is converted to ahphatic esters for use in soaps, perfume, and davors. Benzyl salicylate is used as a sunscreen in lotions and creams. By-product benzal chloride can be converted to benzaldehyde, which is also produced directiy by oxidation of toluene and as a by-product during formation of benzoic acid. By-product ben zotrichl oride is not hydrolyzed to make benzoic acid but is allowed to react with benzoic acid to yield benzoyl chloride. 

Continuous chlorination of benzene at 30—50°C in the presence of a Lewis acid typically yields 85% monochlorobenzene. Temperatures in the range of 150—190°C favor production of the dichlorobenzene products. The para isomer is produced in a ratio of 2—3 to 1 of the ortho isomer. Other methods of aromatic ring chlorination include use of a mixture of hydrogen chloride and air in the presence of a copper—salt catalyst, or sulfuryl chloride in the presence of aluminum chloride at ambient temperatures. Free-radical chlorination of toluene successively yields benzyl chloride, benzal chloride, and benzotrichloride. Related chlorination agents include sulfuryl chloride, tert-huty hypochlorite, and /V-ch1orosuccinimide which yield benzyl chloride under the influence of light, heat, or radical initiators. 

In the pyrrole series, ester groups a to nitrogen are more readily hydrolyzed by alkali, but those in a /3 position more readily by acid. A methoxycarbonyl group in the 2-positlon is meta directing thus bromination yields mainly 4-bromo-2-methoxycarbonylpyrrole. Free radical chlorination with f-butylhypochlorite gives the 5-chloro derivative. 

Radical chlorination reactions show a substantial polar effect. Positions substituted by electron-withdrawing groups are relatively unreactive toward chlorination, even though the substituents may be potentially capable of stabilizing the free-radical intermediate " ... 

Photochemical brominations offluorobenzene or difluorobenzenes produce hexabromocyclohexane derivatives in low yield. Tri- and tetrafluorobenzenes are unreactive under these conditions [17 (Table 6). Analogous free-radical chlorination of benzotrifluoride produces a 9% yield of the hexachloro adduct [iS]... 

Methyl radical Chlorine atom Combination of two methyl radicals ... 

Chloromethyl radical Chlorine Dichloromethane Chlorine atom... 

What are the three products resulting from free-radical chlorination of toluene Why are only three hydrogens replaced ... 

The production of adiponitrile from butadiene starts by a free radical chlorination, which produces a mixture of 1,4-dichloro-2-butene and 3,4-dichloro -1-butene ... 

Problem 5.2 Radical chlorination of alkanes is not generally useful because mixtures of products often result when more than one kind of C-H bond is present in the substrate. Draw and name all monochloro substitution products CgM 13CI you might obtain by reaction of 2-methylpentane with C)2. 

Radical chlorination of pentane is a poor way to prepare 1-chloropentane, but radical chlorination of neopentane, (CI- C, is a good way to prepare neopentyl chloride, (CHj CO Cl. Explain. 

Despite the limitations of radical chlorination of alkanes, the reaction is still useful for synthesizing certain halogenated compounds. For which of the following compounds does radical chlorination give a single moiiochloro product ... 

Figure 10.1 Mechanism of the radical chlorination of methane. Initiation step Three kinds of steps are required initiation, propagation, and termination. The propagation steps are a repeating cycle, with Cl- a reactant in step 1 and a product in...

What are the reasons for the observed reactivity order of alkane hydrogens toward radical chlorination A look at the bond dissociation energies given previously in Table 5.3 on page 156 hints at the answer. The data in Table 5.3 indicate that a tertiary C—H bond (390 kj/mol 93 kcal/mol) is weaker than a secondary C-H bond (401 kj/mol 96 kcal/mol), which is in turn weaker than a primary C H bond (420 kj/mol 100 kcal/mol). Since less energy is needed to break a tertiary C-H bond than to break a primary or secondary C-H bond, the resultant tertiary radical is more stable than a primary or secondary radical. 

Problem 10.3 Draw and name all monochloro products you would expect to obtain from radical chlorination of 2-methylpentane. Which, if any, are chiral ... 

Draw and name the monochlorination products you might obtain by radical chlorination of 2-inethylbutane. Which of the products are chiral Are any of the products optically active ... 

Assume that you have carried out a radical chlorination reaction on (P)-2-chloro-pentane and have isolated (in low yield) 2,4-dichIoropentane. How many stereoisomers of the product are formed and in what ratio Are any of the isomers optically active (See Problem 10.24.)... 

Chain reaction (Section 5.3) A reaction that., once initiated, sustains itself in an endlessly repeating cycle of propagation steps. The radical chlorination of alkanes is an example of a chain reaction that is initiated by irradiation with light and then continues in a series of propagation steps. 

Initiator (Section 5.3) A substance with an easily broken bond that is used to initiate a radical chain reaction. For example, radical chlorination of alkanes is initiated when light energy breaks the weak Cl-Cl bond to form Cl-radicals. 

An industrial investigation studied the radical chlorination of alkanes in micro heatexchangers toanalyse thermal effects onradical production [29,30]. Itwas knownfrompriorstudiesinareactorconsistingoftwoconventionaltubes.onefor... 

M. L. Poutsma, Free-Radical Chlorination of Organic Molecules, in Methods in Free-Radical Chemistry (Ed. E. S. Huyser), Vol. 1, Marcel Dekker, New York, 1969, pp. 79-193. 

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