Cyclic chlorinated compounds

21 Hexachlorocyclohexane (HCH). Hexachlorocyclohexane (HCH), also known as benzene hexachloride (BHC), was discovered in England and France independently in 1942. It consists of five isomers (a, P, y, 8, and e), but only the y isomer exhibits pronounced insecticidal properties, which account for 12% of the total (Table 4.2). The purified y isomer is called lindane. HCH tends to have an unpleasant musty odor, and this odor gives an off-flavor to root and tuber crops, which limits its agricultural use. Conversely, lindane is odorless, so it is the commercial form used currently. It is still used in the control of lice and fleas on humans, livestock, and pets. In 2002, it was banned from food-related uses. 

Note a bond = axial bond (above or below the plane) V bond = equatorial 

The oral LD50 values of these insecticides in rats are aldrin, 38-67 mg/kg dieldrin, 37-87 mg/kg chlordane, 367-515 mg/kg endrin, 7-15 mg/kg heptachlor, 147-220 mg/kg endosulfan, 18-43 mg/kg chlordecone, 114-140 mg/kg mirex, 306 mg/kg and toxaphene, 69 mg/kg. Thus, the cyclodienes vary widely in mammalian toxicity. 

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Dioxins chlorinated cyclic compounds Dipeptide two amino acids joined a peptide bond... 

E is facile. Dehydrochlorination provides the aromatic products 233. An alternatively possible HC1 elimination/electrocyclization/decarboxylation pathway was excluded, since lactone 230B was thermally stable under the reaction conditions in the absence of the catalyst. (NHC)Cu(I) catalyst 232 gave comparable or better yields than 231 in these ATRC/ring contraction sequences, while other (NHC)Cu(I) complexes provided considerably lower yields [320]. Chlorinated cyclic compounds arising from ATRC can also be transformed to chlorinated furans [321]. 

The same procedure applies also to the following partly chlorinated cyclic compounds ... 

In many cases, the yields of these products are high. However, the use of /V-silylated triazoles as nucleophiles or the use of cyclic nitroso acetals (475) substituted at the C-3 atom leads to a noticeable decrease in the yield of the oximes. Therefore, steric hindrance in nitroso acetals and a decrease in nucleophilicity of A-centered nucleophiles result in an increase in the contribution of side reactions. It should be emphasized that C -nucleophiles, such as anions of nitro compounds, are not involved in coupling reactions with cyclic nitroso acetals (475). However, the products, which formally correspond to the C,C-coupling mechanism, can be prepared by the nucleophilic substitution of chlorine in compound (476 d) by a Sa/2 mechanism (Scheme 3.254, product (483c), the yield was 79%). 

Chloracne is highly specific sign, occurring under contact with chlorinated cyclic organic compounds only. Period of affection lasts from several months till several years, depending on degree of poisoning. 

The only six membered hetero-cyclic compound which we shall consider is the one analogous to pyrrole. It contains a hetero-cyclic ring of five carbons and one nitrogen just as pyrrole contains four carbons and one nitrogen. This compound is known as pyridine. That pyridine is a six membered ring analogous to pyrrole is proven by the fact previously referred to (p. 854), that potassium pyrrole by the action of chloroform takes up an additional carbon and yields a chlorine substitution product of pyridine. 

They may be differentiated from other chlorinated hydrocarbon compounds (e.g., solvents) by molecular weight. Organochlorine insecticides, by virtue of their cyclic structure, have molecular weights ranging from 291 to 545, whereas chlorinated hydrocarbon solvents and fumigants have molecular weights that generally are less than 236. 

Structure (33) has been assigned to the product obtained when PC15 reacts with the sodium salt of methane tricarbonitrile, NaC(CN)3 similar reactions occur when the PC15 is replaced by PhnPCl5 , where n = 1 or 3.330 However, if the silver salt of the nitrile is used, a cyclic compound (34) is obtained in addition to (33). Chlorine elimination occurs when N-l-cyano-alkyl-P-phenylphosphonimidic chlorides are prepared according to equa-... 

Summaries of three-dimensional solubility parameters are given by Hansen and Beerbower (21) and by Hoy (22). A problem that now arises, however, and that is of real significance, is the fact that the three-dimensional parameters tabulated by Hansen and Beerbower and by Hoy do not always agree. This disagreement is illustrated in Table I for three common solvents, chosen at random from the source tables. An additional problem, noted by Hansen, is that the homomorph concept for estimating 6j fails in cases of solvents containing chlorine or sulfur atoms, and, in addition, homomorphs for cyclic compounds are hard to find. 

Cyclic compounds undergo the same reactions as acyclic compounds. For example, cyclic alkanes, like acyclic alkanes, undergo radical substitution reactions with chlorine or bromine. 

Many of the most widely used chlorinated cyclic hydrocarbon compounds have been found to be carcinogenic in experimental laboratory rodents (Table I). 

Condensation of 102c with symmetric or mixed (allyl, trimethylsilylethyl) ketomalonic esters gave the carbinolamides 283, which were reduced to 285 by chlorination (SOCl2/pyridine) and treatment with zinc (i-PrOH, AcOH in CH2CI2 concomitant TCE removal). The silver thiolates 286, obtained by tritylthio cleavage under the usual conditions, reacted with thiocarbonyldiimi-dazole to produce the cyclic compounds 288 directly. Mono-deprotection with... 

The B bands of the cyclic compounds (Via) and (VIb) exhibit the most dramatic bathochromic shifts, thus suggesting that the deformation of the aromatic nuclei and some transannular interaction of the two aromatic rings is a feature which persists also in the disiloxane-bridged polyhalo-aromatic derivatives of type (VI). The replacement of chlorine for fluorine atoms in the aromatic nuclei also has a pronounced effect upon the ultraviolet absorption spectrum, resulting in a broadening of the B band, disappearance of the fine structure and a strong hypsochromic effect upon the band. 

Systematic investigations of substituted naphthoxyacetic acids have been carried out rather recently only and the most important data have been summarized by Luckwill and Woodcock . From their work (with the tomato ovary test) it appears that chlorine substitution in 2-NOA in the 3-position only is compatible with an activity similar to that of the parent acid itself. Substitution at i-, 4- or 5-positions results in a practically complete inactivation. This emphasizes again that substitution in bi-cyclic compounds is rather generally less effective (or even undesirable) than in the phenyl and phenoxy series. Although possibly more complicated, an overweighting of the lipophily of the molecule may play an important part. 

Si-fluorinated C-chlorinated cyclocarbosilanes have been produced in good yield by chlorination of the CH2 groups of the corresponding cyclic compounds [189]. 

In connection with the conversion of partly chlorinated cyclic carbosilanes, the reaction between (Cl2Si— 12)3 and (H2Si—CH2)3 is of special interest. The reaction performed in a mole ratio of 1 1.1 in benzene proceeds to the compounds shown in Table 33. Of the 95% of (H2Si—CH2)3 which was chlorinated, 63% underwent formation of one SiHCl group and 37 % underwent formation of two SiHCl groups. 

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