A CHEMICAL STUDY OF THE HALOGENATION OF SELECTED TERPENES (original) (raw)
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Journal of The American Chemical Society, 1975
Both groups attribute smooth curvature in log rate Constant vs. log aHB plots to variation in log (fsn+/f+). (31) Note that we are taking a ratio of activity coefficients and then the log of that ratio which greatly helps to even out nonlinear behavior. Abstract: Irradiation of exo-tricyclo[3.2.1 .02s4]octane and tert-butyl hypochlorite at 4 0 ' in CC14 generates a mixture of monochlorides which consists of exo-6-chloro-, endo-6-chloro-, and l-chloro-exo-tricyclo[3.2.1 .02s4]octane in a ratio of 67: 12: 17. In contrast, radical chlorination of endo-tricyclo[3.2.1 .02.4]octane with tert-butyl hypochlorite results in a mixture of monochlorides consisting of anti-8-chloro-endo-tricyclo[3.2.1 .02*4]octane, endo-2-chlorotricyclo[3.3.0.04~6]octane, and two incompletely characterized components in a 66:27:5:2 ratio. Analogous radical chlorination of exo,exo-tetracyclo[3.3.1.-02.4.06.8]nonane with tert-butyl hypochlorite yields 1-chloro-and 2-chlorotetracyclo[3.3.1 .02~4.06~8]nonane in a ratio of 71: 22, while photochlorination of exo,endo-tetracyclo[3.3.1.0*~4.06~*]nonane with tert-butyl hypochlorite gives 1-chloro-and 6chloro-exo,endo-tetracyclo[3.3.1 .02.4.06~8]nonane and endo-9-chloro-exo-tetracycl0[4.3.O.O*~~.0~~~]n0nane in a ratio of 44:
Tetrahedron Letters, 1994
Methyl cechlon-~ or a,adichloroastars are cbtained in excellent yields by oxidation chlorination of 2-alkyl-4,S-dimethyl-1,3-dioxolanes with trichl~socyanuric acid Esters of a,a-dichloro-carboxylic acids are use&l intemu&tes in the preparation of a-chloro-esters1 and of glycidic esters,2~3 through the Darzens reaction. General procedures for the synthesis of these dihaloeaters have been till now limited to the alkylation of dichloroacetates3 and to the Hell-Volhard-Zelinakii chlorination of carboxylic acids.5 However, the former method, though being more versatile, follows a very complicated procedure and the second one uses drastic reaction conditions. A preparation of a,a-dihaloesters by halogenation of ketene thioacetals has been alao reported, but without experimental detaih~ and yields.5
Chemistry of N-halamines. XVI. Chlorination of alkenes with trichloramine
Journal of Organic Chemistry, 1971
Trichloramine in nonpolar solvent gave excellent yields of vicinal dichlorides with certain types of olefins. Nitrogen was generated almost quantitatively, along with the by-products, ammonium chloride and basic material. With 1-hexene, 1-octene, cyclopentene, cyclohexene, 3-chloropropene, and 1,1-dichloroethylene as substrates, yields of the corresponding vic-dichlorides ranged from 89 to 97%. The meso:dZ ratios for chlorination of the isomeric 2-butenes were similar to those obtained from molecular chlorine under radical conditions. Additional evidence for a radical mechanism was derived from relative reactivities, catalysis, formation of some cis-1,2dichlorocyclohexane from cyclocyclohexene, and participation of an alkane additive. The high addition: substitution ratios suggest that free chlorine atoms are generated in no more than minor amounts. The detailed aspects of the radical pathway are discussed.
The Journal of Physical Chemistry A, 1999
Cavity ring-down spectroscopy (CRDS), end-product analysis, and ab initio calculations have determined absorption cross sections, rate coefficients, reaction mechanisms, and thermochemistry relevant to the addition of halogen atoms to propargyl chloride and propargyl bromide. Halogen atoms were produced by laser photolysis, and the addition reaction products were probed at a variable delay by CRDS using a second laser pulse. We report the continuum spectra of C 3 H 3 Cl 2 (1,2-dichloroallyl), C 3 H 3 ClBr (1-chloro-2-bromoallyl), and C 3 H 3 Br 2 (1,2-dibromoallyl) radicals between 238 and 252 nm and the absorption cross sections, σ 240 (C 3 H 3 -Cl 2 ) ) (4.20 ( 1.05) × 10 -17 cm 2 molecule -1 and σ 242 (C 3 H 3 Br 2 ) ) (1.04 ( 0.31) × 10 -17 cm 2 molecule -1 . When the observed data are fit to complex reaction schemes, the 298 K rate coefficients for formation of 1,2-dihaloallyl radicals at 665 Pa were found to be k(Cl + C 3 H 3 Cl) ) (1.2 ( 0.2) × 10 -10 cm 3 molecule -1 s -1 and k(Br + C 3 H 3 Br) ) (2 ( 1) × 10 -12 cm 3 molecule -1 s -1 . At 298 K and 665 Pa the self-reaction rate coefficients of these radicals were found to be k(C 3 H 3 Cl 2 + C 3 H 3 Cl 2 ) ) (3.4 ( 0.9) × 10 -11 cm 3 molecule -1 s -1 and k(C 3 H 3 Br 2 + C 3 H 3 Br 2 ) ) (1.7 ( 1.1) × 10 -11 cm 3 molecule -1 s -1 . The listed uncertainties are twice the standard deviation of individual determinations, and those for rate coefficients include the uncertainty of the appropriate absorption cross section. † NIST/NRC Postdoctoral Associate 1995-1997.
New routes to 1,1-dichloro-4-methyl-1,3-pentadiene
Tetrahedron, 1984
1, l, l-trichloro-Z-hydroxy-4-methyl-pentene-3 lb) was chlorinated to afford tri-and tetra-chlorinated compoun & s 2,3,4. Compounds 2 and 2 were transformed by reductive dechlorinatioii into l,l,-aichloro-4-methyl-1,3-pentadiene @JJ. Another route starting from the same alcohol or its isomer was also developed.
Reactions of t-acetylenic halides with grignard reagents
Tetrahedron, 1965
The diacetylenic chloride, 6chlorcFdmethyl-2&heptadiyne (I) reacted with methylmagnesium bromide to give a complex mixture of products, including the allene, 2-methyl-2,3heptadien-5-yne (III). The treatment of the acetylenic dichloride, 2,5dichloro-2,5-dimethyl-3hexyne (VI) with methylmagnesium bromide gave the cumulene, 2,Sdimethyl-2,3,4atriene (VII), and a similar reaction with 2,7-dichloro-2,7dimethyl-3,S+ctadiyne yielded the extremely unstable cumulene, 2,7dimethyl-2,3,4,5&octapentaene (XII). The formation of these compounds can be explained by a functional exchangeelimination mechanism involving radicals.
The free radical reaction between alkanes and carbon tetrachloride
Journal of the American Chemical Society
Product studies and kinetic electron paramagnetic resonance methods were used to investigate the free radical reaction between alkanes and carbon tetrachloride in solution. Trichloromethyl radicals abstracted hydrogen from simple alkanes with rate constants of ca. 60 M-I C1 at 300 K, in good agreement with gas-phase data. However, rate constants for chlorine abstraction by alkyl radicals from carbon tetrachloride were ca. lo4 M-I S-I and were therefore ca. 2 orders of magnitude higher in solution than in the gas phase. Possibilities for the origin of this effect a r e discussed.