Formation of three-membered rings by SHi displacement. Reverse of cyclopropyl ring opening

Article abstract of DOI:10.1021/jo960879u

The general methods, photoinitiated or peroxide-initiated free radical chain additions of halomethanes to olefins, yield 1,2-addition products at temperatures ranging from 20 to 100°C. At lower temperatures, -42 to -104°C, a competitive reaction, subsequent to the addition of CCl₂X^., yields alkylcyclopropanes. The reactions of 1-octene or 1-hexene and 1-methylcyclohexene with atomic hydrogen carried out in the presence of several transfer agents (CCl₄, CCl₃Br, CCl₂Br₂) initiate a radical chain addition of CCl₂X^. and yield cyclized materials resulting from the S_Hi displacement of halogen by a carbon-centered radical. The radical displacement of a halogen on carbon, the reverse of homolytic displacement on cyclopropyl carbon, is dominant at low temperatures. The rate constants for cyclization (k_c) vs transfer with halomethane (k_t) showed isokinetic temperatures of -46°C (CCl₄, 1-hexene); -35°C (CCl₄, 1-methylcyclohexene). The isokinetic temperatures for the reactions of the two substrates carried out in the presence of BrCCl₃ were calculated as -204 °C (1-octene) and -109°C (1-methylcyclohexene).

Full text of DOI:10.1021/jo960879u

6818
J . Org. Chem. 1996, 61, 6818-6824
F or m a tion of Th r ee-Mem ber ed Rin gs by SHi Disp la cem en t.
Rever se of Cyclop r op yl Rin g Op en in g1
Dennis D. Tanner,* Liying Zhang, Li Qing Hu, and Pramod Kandanarachchi
Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2
Received May 14, 1996X
The general methods, photoinitiated or peroxide-initiated free radical chain additions of halom-
ethanes to olefins, yield 1,2-addition products at temperatures ranging from 20 to 100 °C. At lower
temperatures, -42 to -104 °C, a competitive reaction, subsequent to the addition of CCl2X•, yields
alkylcyclopropanes. The reactions of 1-octene or 1-hexene and 1-methylcyclohexene with atomic
hydrogen carried out in the presence of several transfer agents (CCl4, CCl3Br, CCl2Br2) initiate a
radical chain addition of CCl2X• and yield cyclized materials resulting from the SHi displacement
of halogen by a carbon-centered radical. The radical displacement of a halogen on carbon, the
reverse of homolytic displacement on cyclopropyl carbon, is dominant at low temperatures. The
rate constants for cyclization (kc) vs transfer with halomethane (kt) showed isokinetic temperatures
of -46 °C (CCl4, 1-hexene); -35 °C (CCl4, 1-methylcyclohexene). The isokinetic temperatures for
the reactions of the two substrates carried out in the presence of BrCCl3 were calculated as -204
°C (1-octene) and -109 °C (1-methylcyclohexene).
The mechanisms for the regioselective additions of
methylcyclohexane, hexachloroethane, and the dimeric
compound 1,1′-dimethyl-1,1′-bicyclohexyl), an additional
chlorine- containing product, 7,7-dichloro-1-methylbicyclo-
[4.1.0]heptane, was formed, see Table 1.
atomic hydrogen to 1-octene2 and 1-methylcyclohexene1,3
were recently reported. Hydrogen atoms generated in a
flow system using a microwave plasma and passed in a
stream over a stirred solution of the substrate, either
neat or in solvent acetone, yield a mixture of reduction
products. The additions were found to be highly regi-
oselective (i.e., H• added exclusively to the least highly
substituted end of the double bond).2,3
Rea ction s in th e P r esen ce of CCl4 a n d CCl3Br . In
preliminary experiments, in order to substantiate whether
atomic hydrogen added exclusively to the 2-position of
1-methylcyclohexene (eq 1), the reactions were carried
out in acetone containing varying concentrations of a
transfer agent, carbon tetrachloride. Although atomic
hydrogen reacts with carbon tetrachloride (eq 2) to yield
HCl, C2Cl6, and CCl3H, its reaction with olefins is much
faster, since only small amounts of HCl could be detected.
Alkyl radical abstraction of a chlorine atom to form the
trichloromethyl radical (eq 3) accounts for 82-100% of
the products formed from the reactions involving carbon
tetrachloride. The product distribution of the reactions
is shown in Table 1. The HCl that was detected by
titration, however, did not react with the olefin since
control experiments showed that no reaction occurred
between 1-methylcyclohexene and HCl under the experi-
mental conditions (neat olefin, -78 °C, 30 min). Since
the only monochlorinated product was 1-chloro-1-meth-
ylcyclohexane (i.e., no 2-chloro-1-methylcyclohexane could
be detected), the addition of H• appeared to take place
at the secondary carbon of the double bond (e.g., eqs 1
and 3). In addition to the expected products (chloroform,
methylcyclohexane, methylenecyclohexane, 1-chloro-1-
Since atomic hydrogen reacts by addition to the least
hindered olefinic position, eq 1, and the tertiary alkyl
radical reacts with carbon tetrachloride, eq 3, both
products of the tertiary alkyl radical and the CCl3• radical
are predictably formed. The CCl3• radical is also formed,
but more slowly, by the reaction of atomic hydrogen with
CCl4, eq 2.
The unexpected product, 7,7-dichloro-1-methylbicyclo-
[4.1.0]heptane appears to be the result of a radical
displacement on carbon (eq 4). Although examples of this
reaction type are rare, they are not unprecedented.
J ohnson et al.4,5 reported that two isomeric 1-cyano-2,2-
dimethyl-3-(2′,2′,2′-trichloroethyl)cyclopropanes were
formed through a radical cyclization pathway from the
reactions of 2-bromo-3,3-dimethyl-4-pentenenitrile with
* Tel: 403-492-3512. Fax: 403-492-8231. e-mail: dennis.tanner@
ualberta.ca.
X Abstract published in Advance ACS Abstracts, September 1, 1996.
(1) Taken in part from the Ph.D. Dissertation of L. Zhang, Univer-
sity of Alberta, 1994.
(4) Bury, A.; Corker, S. T.; J ohnson, M. D. J . Chem. Soc., Perkin
(2) Tanner, D. D.; Zhang, L. J . Am. Chem. Soc. 1994, 116, 6683.
(3) Tanner, D. D.; Zhang, L.; Kandanarachchi, P. J . Phys. Chem.
1996, 100, 11319.
Trans. 1 1982, 645.
(5) Bury, A.; J ohnson, M. D. J . Chem. Soc., Chem. Commun. 1980,
498.
S0022-3263(96)00879-1 CCC: $12.00 © 1996 American Chemical Society

Formation of Three-Membered Rings by SHi Displacement
J . Org. Chem., Vol. 61, No. 20, 1996 6819
Ta ble 1. P r od u ct Distr ibu tion fr om th e Rea ction of Atom ic Hyd r ogen w ith 1-Meth ylcycloh exen e (-78 °C) in th e
P r esen ce of Ca r bon Tetr a ch lor id ea
a
b
The concentration of 1-methylcyclohexene is 1.00 M in acetone. Trace of HCl was detected. c Products arising from the dispropor-
tionation of the 1-methyl-6-(trichloromethyl)cyclohexyl radical were detected in ∼1:0.4:0.9 ratio (1-methyl-2-trichlorocyclohexene,
1-methylene-2-(trichloromethyl)cyclohexane, 1-methyl-6-(trichloromethyl)cyclohexene).
Ta ble 2. P r od u ct Distr ibu tion fr om th e Rea ction s of H• w ith 1-Meth ylcycloh exen e in th e P r esen ce of CCl4 (4 M)a
a
Concentration of 1-methylcyclohexene is 1.060 M in acetone.
carbon tetrachloride, bromotrichloromethane, or trichlo-
romethanesulfonyl chloride, eq 5. A similar cyclization
surprising since the rate of transfer of the sterically hind
ered tertiary radical is expected to be much slower than
that of an intramolecular displacement-cyclization.4-7
was also reported6 which involved an SHi displacement
of cobaloxime by a carbon-centered radical, eqs 6 and 7.
In order to increase the possibility that the transfer rate
kt[CCl4], will compete with the rate of cyclization, the
concentration of [CCl4] was increased to 4 M, see Table
2. Under these conditions both the cyclized product and
the 1,2-addition product are formed. An even higher
ratio of 1,2-addition/cyclization product is obtained when
bromotrichloromethane, a more favorable halogen donor,
is used as a transfer agent, see Table 3.
The cyclization mechanism was further substantiated
by carrying out the hydrogenation of 1-hexene in the
The observation that at -78 °C ring closure, kc, takes
place (eq 4) in preference to 1,2-addition, kt, (eq 8), is not
(7) (a) The transfer rate constant for a primary radical7b with CCl4
at -78 °C is 8 × 101 and would be even slower with a tertiary radical.
A transfer rate, kt[CCl4], at these concentrations would not be expected
to propagate a chain. (b) Newcomb, M. Tetrahedron 1993, 49, 1151.
(6) J ohnson, M. D. Acc. Chem. Res. 1983, 16, 343.

6820 J . Org. Chem., Vol. 61, No. 20, 1996
Tanner et al.
Ta ble 3. Rea ction of 1-Meth ylcycloh exen e (1.06 M) w ith H• in Solven t Aceton e w ith Ad d ed Br CCl3 (1.06 M)
Ta ble 4. P r od u ct Distr ibu tion fr om th e Rea ction s of Atom ic Hyd r ogen w ith 1-Hexen e in th e P r esen ce of Ca r bon
Tetr a ch lor id e (2 M).
presence of CCl4 or of 1-octene in the presence of BrCCl3.
The addition of a trichloromethyl radical to the terminal
position of a monosubstituted olefin yields a secondary
alkyl radical. Since the secondary alkyl radical is more
reactive and less sterically crowded than the tertiary
radical formed from the addition of CCl3• to 1-methylcy-
clohexene, it is predictable that a higher ratio of 1,2-
addition, P12, of CCl3X to cyclization, Pc, can be achieved.
The ratios of P12/Pc obtained from the analysis of the
reaction mixture from 1-octene and 1-hexene are listed
in Table 4 and 5.
disproportionation products, another pathway for the
formation of the cyclopropane can be envisioned. Dis-
proportionation between two molecules of i could also
lead to a cyclized product, eq 11. This pathway, although
To test the hypothesis that the three-membered-ring
system was formed via a radical displacement, 3-bromo-
1,1,1-trichlorononane was synthesized and allowed to
react with atomic hydrogen. Since it had previously been
demonstrated that a secondary alkyl bromide readily
reacts with atomic hydrogen,2 it was assumed that
radical displacement of bromine would likely form the
secondary radical, i. As predicted, 1,1-dichloro-2-hexy-
lcyclopropane resulting from the reaction of radical i was
formed, although not as the exclusive product, eqs 9 and
10. Since a majority of the products formed from i are
plausible, can be ruled out since no tetrachlorinated
product could be detected. This conclusion, that the
cyclized material was not a product of disproportionation,
was further substantiated since in reactions carried out
with CCl3Br no CCl4 could be detected (see eq 12).

Formation of Three-Membered Rings by SHi Displacement
J . Org. Chem., Vol. 61, No. 20, 1996 6821
Ta ble 5. P r od u ct Distr ibu tion of th e Rea ction of Atom ic Hyd r ogen w ith 1-Octen e in P r esen ce of
Br om otr ich lor om eth a n e
a
b
BrCCl3 in neat 1-octene. BrCCl3 in 3 M solution of 1-octene in acetone. c R ) C6H13, R′ ) C5H11
.
of vinyl acetate (see eq 14).10 where ∆Ea ) Ea(t) - Ea(p)
)
9.08 kcal mol-1 for CCl4 and 1.1 kcal mol-1 for BrCCl3.
Since the Arrhenius equation for the polymerization
propagation reaction, kp ) 2.0 × 106 exp(-4700/RT) M-1
s-1, has also been reported,11 the temperature dependence
of the transfer rate constant is determined, see Table 6.
Also listed in Table 6 is a comparison of the experimental
and calculated ratios of rate constants of cyclized/1,2-
addition products.
The homolytic 1,2-addition to olefins of both CCl4 and
CCl3Br are standard synthetic reactions.8,9 No geminal
dichlorocyclopropanes have been reported as products
from these additions. The standard conditions used in
these synthetic reactions prescribe reaction between a
2:1 mixture of CCl3X:olefin (CCl4, 90-100 °C, benzoyl
peroxide) or (CCl3Br, 60-70 °C, acetyl peroxide or hν).
At -78 °C the cyclization reaction for CCl4 is favored
over 1,2-addition, see Tables 4 and 5. Since it appears
that the temperature at which the two competing reac-
tions (addition and cyclization) are carried out could be
the major factor determining the ratio of these two
products, the temperature dependence of their formation
was determined. At -78 °C the cyclization reaction for
CCl4 is favored over 1,2-addition; this temperature ap-
pears to be lower than the isokinetic temperature at
which the two rates become equal or reversed. When the
reaction was carried out at several temperatures, a plot
of the activation energy differences for addition vs
cyclization could be calculated. As suspected, the ratio
of rate constants is reversed at the isokinetic tempera-
ture: -46 °C (CCl4, 1-hexene); -35 °C (CCl4, 1-methyl-
cyclohexene), see Figure 1, part a.
Arrhenius plots of the rates of cyclization of the
•
radicals resulting from the addition of CCl3 to 1-octene
or 1-hexene and 1-methylcyclohexene (Figure 2) gener-
ated from either transfer agent (CCl4 and CCl3Br) can
be constructed.
The activation parameters for cyclization, calculated
from the experimental data (Table 6), for either the (2,2,2-
trichloroethyl)heptyl or the (2,2,2-trichloroethyl)pentyl
radical (EC ) 6.6 ( 0.76 kcal/mol; log AC ) 9.7 ( 0.9 eu)
generated in the presence of CCl4 or CCl3Br are consis-
tent with cyclization reactions where only 2° of rotational
freedom are frozen in the transition state.12 The rate
constant for cyclization, using these activation param-
eters, was kc(25 °C) ) 9.4 × 104 s-1, regardless of which
transfer agent was used. An analysis of the activation
parameters calculated for the cyclization of the 1-methyl-
2-(2′,2′,2′-trichloromethyl)cyclohexyl radical (EC ) 3.2 (
0.8 kcal/mol; log AC ) 7.4 ( 0.1 eu), see Table 6 and
Figure 2, was less straight forward since the transition
state rigidity for the reaction of a substituted cyclohexyl
radical could not be well defined.13 The rate constant
obtained for the substituted cyclohexyl radical (kc 25 °C)
) 6.4 × 104 s-1) was also insensitive to the transfer agent
used. A possible error in the determination of the
cyclization rate constant could be introduced during the
reaction of BrCCl3 with the olefin, since subsequent to
1,2-addition further reaction (i.e. eqs 10 and 11) of the
bromide with H• could lead to cyclization. This complica-
tion (at low conversion) can be ruled out since kc is
constant for reactions where either CCl3Br or CCl4 is used
as the transfer agent (see Figure 2).
The isokinetic temperature for the hydrogen atom
promoted reaction of BrCCl3 can likewise be determined
for the two substrates: -204 °C (BrCCl3, 1-octene); -109
°C (BrCCl3, 1-methylcyclohexene), see Figure 1, part b.
The cyclization rate constants for both substrates, kc, can
be calculated if the rate constants for transfer, kt, are
known (eq 13). The transfer rate constants, kt, could be
calculated since the temperature dependence of the chain
transfer constants, C° ) kt/kp, has been reported for the
two transfer agents with the secondary radical formed
during the polymerization
(10) (a) Walker, R. W. J . Chem. Soc. A 1968, 2391. (b) Shapiro, J .
S.; Weston, R. E., J r. J . Phys. Chem. 1972, 76, 1669. (c) Clark, T. C.;
Dove, J . E. Can. J . Chem. 1973, 51, 2155.
(11) Matheson, M. S.; Auer, E. E.; Bevilacqua, E. B.; Hart, E. J . J .
Am. Chem. Soc. 1949, 71, 497.
ln[Ct1°/Ct2°] ) ∆Ea(1/T1 - 1/T2)/R
(14)
(12) Benson, S. W. Thermochemical Kinetics, 2nd ed.; Wiley: New
York, 1976.
(13) (a) Green, F. D.; Chu, C. C.; Walia, J . J . Am. Chem. Soc. 1962,
84, 2463. (b) Beckwith, A. L. J .; Lawrence, T. J . Chem. Soc., Perkin
Trans. 1 1980, 1535, and references therein.
(8) Walling, C.; Huyser, E. S. Organic Reactions, Vol. 13; Wiley: New
York, 1963.
(9) Sosnovsky, G. Free Radical Reactions in Preparative Organic
Chemistry Macmillan: New York, 1964.

6822 J . Org. Chem., Vol. 61, No. 20, 1996
Tanner et al.
a
F igu r e 2. Arrheneus plot for the cyclization of 1-methyl-2-
(trichloromethyl)cyclohexyl radical (2), and (2,2,2-trichloroet-
hyl)heptyl radical and (2,2,2-trichloroethyl)pentyl radical, (b).
The dotted line represents the extrapolation of the rate
constant, kc, to 70 and 100 °C.
b
chemistry as the Zn-promoted reduction, this pathway
was likewise ruled out, eq 20. The dual mechanism was
F igu r e 1. (a) Variation of log (kt/kc) with 1/T for the reaction
of 1-hexene (A) and 1-methylcyclohexene (B) with hydrogen
atoms in the presence of carbon tetrachloride. The dotted line
represents the extrapolation to the isokinetic temperature. (b)
Variation of log (kt/kc) with 1/T for the reaction of 1-octene (A)
and 1-methylcyclohexene (B) with hydrogen atoms in the
presence of bromotrichloromethane. The open circles represent
extrapolated values to the isokinetic temperatures.
chosen and substantiated since when dibromodifluo-
romethane was allowed to react with an olefin under the
usual radical conditions (3% benzoyl peroxide, 80 °C, 72
h) only 1,2-addition products were obtained;14 no cyclo-
propanation products were detected. These results did
not appear to be a significant test for the mechanism,
since radical addition of halomethanes under these
conditions do not yield cyclized materials. When difluo-
rodibromomethane was allowed to react with H• and
1-octene (-78 °C), only 1,2-addition could be detected.
In agreement with Wu, et al. the cyclopropanation in
their reaction was no doubt due to the presence of Zn
(eq 18 or 19).
Rea ction in th e P r esen ce of CCl2Br 2. In order to
generalize the mechanism of the cyclization pathway, the
hydrogenations were carried out in the presence of CCl2-
Br2. As expected, both 1,2-addition and cyclization
occurred at low concentrations of transfer agent, CCl2-
Br2, see Table 7.
Rea ction in th e P r esen ce of CBr 2F 2. More recently
Wu et al.14 reported that at 0 °C the Zn-promoted reaction
of dibromodifluoromethane with several olefins gave not
only 1,2-addition but small amounts of difluorocyclopro-
panated addition. The authors proposed a dual mecha-
nism, a radical reaction to give 1,2-addition (eqs 15 and
16) and disproportionation (eq 17) or Zn-promoted reduc-
tion (eq 18 or 19) to give cyclopropanation. Since carbene
addition (eq 20) did not give the same product stereo-
Exp er im en ta l Section
Ma ter ia ls. 1-Methylcyclohexene (Fluka, +99%), carbon
tetrachloride (Aldrich, HPLC grade, +99%), 1-octene (Phillips,
research grade, +99%), 1-hexene (Aldrich, +99%), bromot-
richloromethane, (Aldrich, spectrophotometric grade, +99.5%),
(14) Wu, S. H.; Liu, W. A.; J iang, X. K. J . Org. Chem. 1994, 59,
854.

Formation of Three-Membered Rings by SHi Displacement
J . Org. Chem., Vol. 61, No. 20, 1996 6823
Ta ble 6. Deter m in a tion of th e Tr a n sfer Ra te Con sta n ts a n d Cycliza tion Ra te Con sta n ts Usin g a Mod el Secon d a r y
Ra d ica l, P oly(vin yl a ceta te)
a
b
Values in parentheses are extrapolated from Figure 1 and 2. Calculated from the experimental values (Table 4 and 5), using eq 12.
Ta ble 7. P r od u ct Distr ibu tion of th e Rea ction of Atom ic Hyd r ogen w ith 1-Octen e (-78 °C) in th e P r esen ce of
Dibr om od ich lor om eth a n ea .
a
b
All solutions were in acetone and the hydrogen flow rate was kept at 4 mL/min. The reaction times varied from 3 to 15 min. R )
C6H13; R′ ) C5H11
.
nonane (Phillips, research grade, +99%), and dodecane (Phil-
lips research grade, +99%) were checked for purity (GC) prior
to use.
addition of dichlorocarbene to cyclohexene.15 The product was
isolated in 62% yield: 1H NMR (400 MHz, CDCl3) δ 1.18-
1.42 (m, 8H), 1.64-1.72 (m, 2H), 1.79-1.98 (m, 2H); 13C NMR
(300 MHz, CDCl3) δ 73.18 (s, 1), 32.00 (d, 1), 27.27 (t, 1), 26.61
(s, 1), 25.54 (q, 1), 20.86, 20.13, 18.87 (t, 3). Anal. Calcd for
C8H12Cl2: C, 53.65; H, 6.75. Found: C, 53.60; H, 6.94.
1-Ch lor o-1-m eth yl-2-(tr ich lor om eth yl)cycloh exan e was
prepared by the peroxide-initiated addition of CCl4 to 1-me-
thylcyclohexene (110 °C) according to the literature procedure
Id en tifica tion a n d Ch a r a cter iza tion of th e Rea ction
P r od u cts. Chloroform, methylcyclohexane, methylenecyclo-
hexane, hexachloroethane, 1-bromooctane, 2-bromooctane,
trans- and cis-2-octene, n-octane, n-hexane, 1,1′-dimethylbi-
cyclohexyl,3 dl- and meso-7,8-dimethyltetradecane, and2 7-me-
thylpentadecane2 were identified by a comparison of their
retention times on GC, GC/MS, and GC/IR with either the
following synthesized materials or with available authentic
samples.
reported for the reaction of 1-octene:16a bp 95 °C/0.2 mmHg;
EI+ (GC/MS, VG-70) m/ z 250 (C8H1235Cl337Cl), 248 (C8H12
-
35
7,7-Dich lor o-1-m eth ylbicyclo[4.1.0]h ep ta n e was pre-
pared according to the literature procedure reported for the
(15) Pacaud, R. H.; Allen, C. F. H. Organic Syntheses; Wiley: New
York, 1943; Collect. Vol. 2, p 336.

6824 J . Org. Chem., Vol. 61, No. 20, 1996
Tanner et al.
Cl337Cl) 213, 175, 129, 109, 93, 77, 65, 53, and 41; IR (gas
phase) ν 2931, 2875, 1454, 1388, 1261, 1125, 933, 781 (st), 658,
and 585 cm-1. Anal. Calcd for C8H12Cl4: C, 38.47; H, 4.84.
Found: C, 38.89; H, 4.99.
°C/4 mmHg; 1H NMR (200 MHz, CDCl3) δ 1.00 (t, 3H, J ) 6.8
Hz), 1.10 (m, 1H), 1.25-1.65 (m, 8H); EI+ (GC/MS) m/ z 165.9,
167.9, 169.9. Anal. Calcd for C7H12Cl2: C, 5032; H, 7.24.
35
Found: C, 50.00; H, 7.51. High resolution MS for C7H12Cl2
:
C7H12Cl235: calcd for 166.03160, found 166.03166.
1-Br om o-1-m eth yl-2-(tr ich lor om eth yl)cycloh exan e was
prepared according to the literature procedure reported for the
addition of BrCCl3 to cyclohexene.16b IR (gas phase): ν 2943,
1,1,1,3-Tetr a ch lor oh ep ta n e was synthesized by the per-
oxide-catalyzed addition of CCl4 to 1-hexene:16a yield 36.1%;
bp 58-60 °C/0.3 mmHg. 1H NMR (200 MHz, CDCl3) δ 0.95
(t, 3H, J ) 6.7 Hz), 1.30-2.02 (m, 6H), 3.08-3.35 (AB, oct,
2H); 4.27 (sext, 1H, J ) 5.0 Hz); EI+ (GC/MS) m/ z 236.0, 238.0,
240.0 (M+). Anal. Calcd for C7H12Cl4: C, 35.33; H, 5.07.
Found: C, 35.07; H, 4.97.
2-Ch lor oh exa n e was prepared by the reactions of 2-hex-
anol with thionyl chloride and pyridine using the method of
Brooks and Snyder:19 yield 53%, bp 123 °C (lit.20 123 °C); EI+
m/ z 120.0, 122.0 (M+).
2876, 1454, 1388, 1251, 1128, 929, 885, 777 (st), and 648 cm-1
.
EI+ (GC/MS, VG-70): m/ z 217, 215, 213 (C8H12Cl3) 179, 177,
143, 141, 109, 105, 95, 55, and 41. Bp 100-105 °C/0.2 mmHg.
Attempts to isolate the product showed it to be thermally
unstable (-HBr), since it was always contaminated with small
amounts of olefin. 1H NMR (CDCl3, 200 MHz): δ 1.38-1.78
(m, 4H), 1.84 (s, 3H, CH3), 1.88-2.52 (m, 4H), 2.97 (m, 1H)
ppm. IR (gas phase): ν 2943, 2876, 1454, 1388, 1251, 1128,
929, 885, 777 (st), 648 cm-1. EI+ (GC/MS, VG-70): m/ z 217,
215, 213 (M+ - Br), 179, 177, 143, 141, 109, 105, 95, 55, 41.
The 1,2-addition product was characterized by heating it to
150 °C and distilling to products, a mixture (1:0.20:0.28) of
three olefinic products, bp 76 °C/1-1.25 mmHg: 1-methyl-2-
(trichloromethyl)cyclohexene, 1-methylene-2-(trichloromethyl)-
cyclohexane, and 1-methyl-6-(trichloromethyl)cyclohexene. A
microanalysis (GC/MS) of the isomeric mixture was consistent
with its assignment. EI+ (GC/MS, VG-70): m/ z 212.0, 214.0,
216.0 (M+), 163.0, 165.0, 167.0, 95.0, 67.0, 41.0; m/ z 212.0,
214.0, 216.0 (M+), 141.1, 95.0, 67.0 41.0; m/ z 212.0, 214.0,
1,1,1,3-Tetr a ch lor on on a n e. The addition product was
prepared according to the literature method by the peroxide
catalyzed addition of CCl4 to 1-octene:16a yield 70.3%, bp 94
°C/0.2 mmHg (lit.16a bp 78-79 °C/0.1 mmHg); η20 ) 1.47675
D
(lit.14 η20 ) 1.4770). The H NMR [(200 MH3, CDCl3) δ 0.91
1
D
(t, 3H, J ) 6.7 Hz), 1.30-2.0 (m, 10H), 3.08, 3.10, 3.16, 3.18,
3.24, 3.27, 3.32, 3.35 (AB, 8 peaks, 2H), 4.25 (6 peaks), 1H, J
) 5.0 Hz)] was consistent with the 60 MHz spectra reported
by Burton and Kehoe.21
cis- a n d tr a n s-2-h exen e were prepared as a mixture with
1-hexene from 2-hexanol and H2SO4 (5.8:5.7:1). The products
were identified by a comparison of their GC/IR22 and GC/MS
with those of the authentic materials. EI+ m/ z 84 (M+).
d l- a n d m eso-5,6-d im eth yld eca n e (1:1) a n d 5-m eth y-
lu n d eca n e were prepared as a mixture by allowing neat
1-hexene to react with atomic hydrogen2,3 at -78 °C. The
216.0 (M+), 141.1, 95.1, 81.0, 67.0, 41.0. Anal. Calcd for C8H11
Cl3: C, 45.00; H, 5.19. Found: C, 45.12; H, 5.39.
-
1,1-Dich lor o-2-h exylcyclop r op a n e was prepared accord-
ing to the literature procedure17 and identified by its GC/MS,
GC/IR, 1H NMR, 13C NMR, and APT: 1H NMR (300 MHz,
CDCl3) δ 0.90 (t, 3H, J ) 7 Hz), 1.35 (m, 1H), 1.25-1.40, and
1.42-1.60 (m, 12H); 13C NMR (300 MHz, CDCl3) δ 14.09 (q,
1), 22.64, 26.82, 28.61, 28.98, 30.41, 31.77 (t, 6), 30.97 (d, 1),
61.73 (s, 1); IR (gas phase) ν 2936, 2869, 1460, 1384, 1125,
1046, and 752 cm-1; EI+ (GC/MS, VG-70) m/ z 194, 196, 198
(M+, C9H12Cl2), 166, 152, 138, 123, 102, 83, 70, 56, and 41.
1-Ch lor o-1-m eth ylcycloh exa n e was prepared according
to the literature procedure.18 Distillation gave 1.1 g (81%) of
1-chloro-1-methylcyclohexane: bp 30-31 °C/6 mmHg (lit.17 bp
65.2-65.5 °C/44 mmHg); 13C NMR (300 MHz, CDCl3) δ 23.89
(q, 1H), 23.01, 25.23, 30.03, 41.58 (t, 5H), 72.00 (s, 1H); IR
(gas phase) ν 2944, 2873, 1452, 1383, 1255, 1147, 982, 880,
777, and 682 cm-1; EI+ (GC/MS, VG-70) m/ z 132 (M+, 35Cl),
117, 97, 96, 81, 67, 55, and 41.
1,1,1-Tr ich lor o-3-br om on on a n e was prepared by the
peroxide-catalyzed (Bz2O2) of BrCCl4 (100 °C) in a 50% yield:
bp 90-92 °C, 0.4 mmHg (lit.18 bp 99-102 °C at 0.6 mmHg);
η24D ) 1.4926 (lit.18 η20D ) 1.4943); 1H NMR (CDCl3, 200 MHz)
δ 0.85 (t, 3H, J ) 7.0 Hz), 1.25-1.60 (m, 8H), 1.85-2.10 (m,
2H), 3.12-3.25 (dd, 1H, J ) 4.0 Hz, J ) 16 Hz), 3.35-3.50
(dd, 1H, J ) 4.0 Hz, J ) 16 Hz), 4.25-4.40 (m, 1H).
1
products were identified by their GC/MS and the H NMR of
the mixture. The isomeric mixture was isolated by distillation,
and a microanalysis of the mixture was obtained. Anal. Calcd
for C12H26: C, 84.6l; H, 15.39. Found: C, 84.55; H, 15.44. The
1H NMR of the methyl protons δ 0.94-0.71 were in the same
ratio as the absorption and chemical shift positions as was
found in the corresponding products reported for 1-octene.2
1-Br om o-1-m eth ylcycloh exa n e was prepared from 1-me-
thylcyclohexene (0.050 mol, 4.80 g) and 50 mL of aqueous 48%
HBr. The reaction mixture was stirred under an atmosphere
of N2 for 2 days at 45 °C. The solution was extracted with
hexane, washed with H2O, dried over anhydrous MgSO4, and
filtered, and the filtrate was distilled under vacuum, bp 45-
46 °C/4 mmHg; η25D 1.4496 (lit.23 bp 66.0-66.5/22 mmHg; η25
D
1.4468). Yield 5.31 g (68.7%) of the product 1-bromo-1-
methylcyclohexane. 1H NMR (CDCl3, 200 MHz) δ 2.00-2.14
(m, 4H, 2-CH2), 1.82 (s, 3H, CH3), 1.40-1.78 (m, 6H, 3CH2).
Anal. Calcd for C7H13Br: C, 47.48; H, 7.40. Found: C, 47.41;
H, 7.62.
J O960879U
1,1-Dich lor o-2-bu tylcyclop r op a n e was synthesized by
the addition of dichlorocarbene to hexene:17 yield 55%, bp 60
(19) Brooks, L. A.; Snyder, H. R. Organic Syntheses; Wiley: New
York, 1955; Collect. Vol. 3, p 698.
(16) (a) Kharasch, M. S.; J ensen, F. Y.; Urry, W. H. J . Am. Chem.
Soc. 1947, 69, 1100. (b) Kharasch, M. S.; Reinmuth, O.; Urry, W. H.
J . Am. Chem. Soc. 1947, 69, 1105.
(17) Takahais, M.; Cvetanovic, R. J . Can. J . Chem. 1962, 40, 1037.
(18) Brown, H. C.; Fletcher, R. S.; J ohanneson, R. B. J . Am. Chem.
Soc. 1951, 73, 212.
(20) Arase, A. Bull. Chem. Soc. J pn. 1974, 47, 2511.
(21) Burton, D. J .; Kehoe, L. J . J . Org. Chem. 1970, 35, 1339.
(22) Aldrich/Hewlett Packard Vapor Phase FT-IR Library Rel. 2,
1991 Software Products, Milwaukee, WI.
(23) Goering, H. L.; Abell, P. I.; Aycock, B. F.J . Am. Chem. Soc. 1952,
74, 3588.