Table Of Contentiv
CONTRIBUTORS TO THIS VOLUME
.R BOLTON
Department of Chemistry, Royal and New College, The Bourne Laboratory,
Egham Hill, Surrey TW20 0EX
.W.D BROWN
School of Chemistry, University of Bath, Claverton Down, Bath 2AB YA7
.F.D EWING
Department oCfh emistry, University of Hull, Hull HU6 XR7
A.J. FLOYD
School of Chemistry, University Boaft h, Claverton Down, Bath 2AB YA7
.T.D HURST
Faculty of Science, Kingston Polytechnic, Penrhyrn Road, Kingston upon
Thames, Surrey KT1 2EE
A.M. JONES
Department of Chemical and Life Sciences, Newcastle upon Tyne Polytechnic,
Ellison Building, Newcastle upon Tyne NE1 8ST
.M SAINSBURY
School of Chemistry, University of Bath, Claverton Down, Bath 2AB YA7
.P.S STANFORTH
Department of Chemical and Life Sciences, Newcastle upon Tyne Polytechnic,
Ellison Building, Newcastle upon Tyne NE1 8ST
.W.C THOMAS
Department of Physical and Biological Sciences, Bristol Polytechnic,
Coldharbour Lane, Bristol
Preface to Volume 1A/B
This is the first sub-volume of the second supplement of "Rodd" encompassing the literature
since 1970, the date when the first supplement was published. The rate of growth of the subject
matter in this time has been so great that a decision was taken to subdivide the original chapters thus
to reduce the burden upon individual contributors. The original brief given to authors was that
between 40-50 pages of camera ready text should be devoted to each topic. Once the project was
underway, however, it was soon appreciated that for certain subject areas this was insufficient space
and some chapters in this volume are expanded far beyond their planned length.
Rigid adherence to deadlines is always very difficult for busy chemists and the expansion in
the size of some contributions has added considerably to this problem. Despite this I am most
grateful to all my co-authors for submitting their chapters on time. Two authors Arthur Floyd and
Warner Thomas had an especially arduous task since they were responsible for two chapters each.
One problem of timetabling could not be surmounted and it has become necessary to delay the
publication of Chapter 6 "Nitrogen derivatives of the Acyclic Hydrocarbons". It will be included in a
later sub-volume.
Malcolm Sainsbury
XVII
LIST OF COMMON ABBREVIATIONS AND SYMBOLS USED
A acid
A ikngstr~m units
Ac acetyl
a axial
as, asymm, asymmetrical
at. atmosphere
B base
Bu butyl
b.p. boiling point
,c C concentration
CD circular dichroism
conc. concentrated
D Debye unit, X 1 10-18 e.s.u.
D dissociation energy
D dextro-rotatory; dextro configuration
d density
dec. or decomp with decomposition
deriv, derivative
E energy; extinction; electromeric effect
El, E2 uni- and hi-molecular elimination mechanisms
cB 1 E unimolecular elimination in conjugate base
ESR electron spin resonance
Et ethyl
e nuclear charge; equatorial
f.p. freezing point
G free energy
GLC gas liquid chromatography
g spectroscopic splitting factor, 2.0023
H applied magnetic field; heat content
h Planck's constant
Hz hertz
I spin quantum number; intensity; inductive effect
IR infrared
J coupling constant in NMR spectra
J Joule
K dissociation constant
k Boltzmann constant; velocity constant
kcal kilocalories
M molecular weight; molar; mesomeric effect
Me methyl
m mass; mole; molecule; meta-
m.p. melting point
Ms mesyl (methanesulphonyl)
XVlll
[MI molecular rotation
N Avogadro number; normal
NMR nucleamra gneticr esonance
NOE Nuclear Overhauser Effect
n normal; refractive index; principal quantum number
o ortho-
ORD optical rotatory dispersion
P polarisation; probability; orbital state
Pr propyl
Ph phenyl
P para-; orbital
PMR proton magnetic resonance
R clockwise configuration
S counterclockwise config.; entropy; net spin of incompleted electronic shells;
orbital state
SN 1, SN2 uni- and bi-molecular nucleophilic substitution mechanisms
iNS internal nucleophilic substitution mechanisms
S symmetrical; orbital
see secondary
soln. solution
symm. symmetrical
T absolute temperature
Tosyl p-toluenesulphonyl
Trityl triphenylmethyl
t time
temp. temperature (in degrees centrigrade)
tert tertiary
UV ultraviolet
optical rotation (in water unless otherwise stated)
specific optical rotation
dielectric constant; extinction coefficient
a dipole moment; magnetic moment
aa Bohr magneton
ag microgram
am micrometer
2 wavelength
P frequency; wave number
,X ,dX uX magnetic; diamagnetic and paramagnetic susceptibilities
(+) dextrorotatory
(-) laevorotatory
m negative charge
+ positive charge
Second Supplements ot the 2nd Edition Roofd d's Chemistry
of Carbon Compounds, Vol. IA/B, edited by .M Sainsbury
(cid:14)9 1991 Elsevier ecneicS Publishers ,.V.B madretsmA
Chapter 1
THE SATURATED HYDROCARBONS- ALKANES
D. .F EWING
.1 Introduction
This survey of alkane chemistry coverst he period from 1972 when a review of
this subject last appeared in Rodd. This period began with the oil crisis of 3791
which had a significant impact on the petrochemical industry. Subsequent
political factors of a similar type have kept the oil and petrochemical industries
in a state of flux right up to the present time and this has permeated back to
fundamental chemistry with the result that interest in hydrocarbon chemistry
has never been greater. In particular the study of alkane functionalization has
come from the academic backwaters to become a mainstream activity, the focus
of the interest of many prominent academic and industrial laboratories. Many
thousands of papers have appeared mostly in the last ten years. Although all
important topics are dealt with here the coverage is necessarily selective and this
chapter has a substantially changed emphasis when compared with the
preceding edition.
.2 Sources of alkanes
Oil and gas are obviously still the major sources of hydrocarbons and since the
discovery of new reserves has kept pace approximately with consumption this
situation will still obtain for many decades to come. However gas reserves have
increased faster than oil reserves and hence there is a move towards increased
use of 1 a C feedstock for the chemical and petrochemical industries. Ideally this
requires the conversion of methane directly to higher hydrocarbons, a process
which is not yet commercially viable. The chemistry of methane dimerization
and oligomerization is discussed below. n A alternative is to convert methane to
methanol v/a syngas and then synthesise higher hydrocarbons from that 1 C
source (C.D.Chang, "Hydrocarbons from Methanol", M.Dekker, New York,
1983; "Catalytic Conversion of Synthesis Gas and Alcohols to Chemicals",
R.G.Herman (Ed.), Plenum, New York, 1984). Petrol obtained by this route
accounts for one third of the domestic market in New Zealand (C.J.Maiden,
"Methane Conversion", D.M.Bibby et al. (Eds), Elsevier, Amsterdam, 1988, pl).
This reaction is catalysed by zeolites and by suitable choice of process
conditions the conversion can be tailored to produce ethene, light alkenes or
petrol (gasoline) (S.A.Tabak and S.Yurchak, Catal. Today, 1990, ,6 307).
The utilization of coal as a hydrocarbon source is accomplished by gasification
to form syngas then application of the Fischer-Tropsch reaction to afford a range
of alkane fractions and other chemicals (R.B.Anderson, 'The Fischer-Tropsch
Synthesis", Academic Press, 1984; M.E.Dry, Catal. Today, 1990, ,6 183). This
process has provided petrol, diesel and chemicals for decades in South Africa.
More than %59 of organic chemicals are derived from these primary
hydrocarbon sources and thus the chemistry of the alkanes is of crucial
importance to the world chemical industry.
The use of vegetable oil as a source of hydrocarbons has been of interest for
many years but has been little more than a curiosity until recently. It has now
been shown that a diesel fraction of hydrocarbons can be readily obtained from
soybean oil by hydrocracking at 250- 053 ~ with high pressure hydrogen using
a catalyst which induces hydrogenation and hydrogenolysis (J.Gusmao et al.,
Catal. Today, 1989, ,5 533).
.3 Preparation of alkanes
(a) Reduction of alkenes and alkynes
Synthetic applications of hydrogenation, including the use of supported
catalysts, have been dealt with in several recent books (M.Freifelder, "Catalytic
Hydrogenation in Organic Synthesis: Procedures and Commentary", Wiley,
New York, 1978; P.N.Rylander, "Hydrogenation Methods", Academic Press,
New York, 1985; F.R.Hartley, "Supported Metal Complexes, A New Generation
of Catalysts", D.Reidel Publishing Co., 1985). The work described here is
restricted to the direct formation ofa lkanes. Hydrogenation of an unsaturated
linkage in functionalised compounds is not included although there is much
overlap in methodology.
Homogeneous catalysiso f stereospecific hydrogenation by transition metal
catalysts has been reviewed (R.E.Harmon, S.K.Gupta and J.W.Scott, Chem. Rev.,
73, 1973, ;12 see also D.Valentine and J.W.Scott, Synthesis, 1978, 329).
Applications to simple alkene hydrogenation are few but using a rhodium
catalyst with chiral ligands 2-cyclohexylbutane was obtained in %06
enantiomeric excess (T.Hayashi, M.Tanaka and I.Ogata, Tetrahedron Left., 1977,
295). An interesting water soluble catalyst is obtained from RhCl 3 and the
phosphine (m-NaSO3-C6H4)3P. The exact structure of the active species is
unknown but it is air stable and effective for quantitative hydrogenation in a
biphasic system (ie aqueous solution of catalyst and liquid alkene) using a
standard low pressure hydrogenator (C.Larpent, R.Dabard and H.Patin,
Tetrahedron Lett., 1987, ,82 2507).
Reduction of cobalt or nickel salts with NaBH 4 gives the corresponding metal
borides which are efficient heterogeneous hydrogenation catalysts (reviewed by
R.C.Wade et al., Catal. Rev. Sci. Eng., 1976,14, 211). Nickel boride is often more
effective than the traditional Raney nickel (J.A.Schreifels, P.C.Maybury and
W.E.Swartz, .J Org. Chem., 1981, 46,1263) and cobalt boride is selective for
mono- and di-substituted alkenes and alkynes (J.O.Osby, S.W.Heinzmann and
B.Ganem, .J Am. Chem. Soc., 1986,108, 67). E.C.Ashby and J.J.Lin .J( Org.
Chem., 1978, 43, 2567) have shown that the chlorides of cobalt, nickel or
titanium catalyse the quantitative reduction of alkenes and alkynes with LiAIH .4
With 41CiT greater selectivity is shown for unhindered alkenes (P.W.Chum and
S.E.Wilson, Tetrahedron Lett., 1976,15) and simple lithium hydride with 3 VCI is
specific for the reduction of terminal alkenes (E.C.Ashby and S.A.Noding, .J
Org. Chem., 1980, 45,1041). A heterogeneous catalyst system of similar function
is NaH/Ni(OAc)2/EtONa (or other alcoholate salts). The actual catalytic
species have unknown stoichiometry but are stable and easily prepared and are
not hazardous (J.-J.Brumet, P.Gallois and P.Caubere, .J Org. Chem., 1980, ,54
.)7391
Ionic hydrogenation of a double bond requires a proton donor and a hydride
donor. Since a carbocation is formed initially this reduction is selective for
CF3COOH Et3SiH
R2C---CR 2 ~ R2CH-CR2 +- ~ R2CH-CHR 2
substituted alkenes. This reaction has been reviewed (D.N.Kursanov,
Z.N.Parnes and N.M.Loim, Synthesis, 1974, 633).
A convenient route to alkanes of specific length has been described by
M.C.Whiting and coworkers. It starts with the readily available bromoaldehyde
(1). This aldehyde is reacted with the Wittigr eagent made from the acetal of )1(
to give a 24-carbon bromoacetal (2). Further analogous chain extension steps
and final reductive removal of double bonds and functional groups has afforded
a range of alkanes up to 287H093C (I.Bidd et al., .J Chem. Soc., Perkin Trans. ,1
1983, 1369; .J Chem. Soc., Chem. Commun., 1985, 543).
Br(CH2)11CHO Br(CH2)I 1CH~-CH(CH2 2)tEO(HC01)
)1( )2(
Further studies of this synthetic strategy (E.Igner et al., .J Chem. Soc., Perkin
Trans. 1,1987, 2447; I.Bidd, D.W.Holdup and M.C.Whiting, C.Jhem. Soc.,
Perkin Trans. ,1 1987, 2455) have resulted in some modifications which give
improved yields and minimise the contamination with compounds of shorter
chain length. Another modification (E.A.Adegoke et al., .J Chem. Soc., Perkin
Trans. ,1 1987, 2465) allows the introduction of lateral alkyl substituents. The
properties of many of the compounds longer than 05C indicate folding of the
chain.
(b) From alkyl halides and alcohols
The substitution of a halogen atom by a hydrogen atom is a reaction of great
importance and can be effected by a bewildering variety of reagents. An
excellent review of this area (A.R.Pinder, Synthesis, 1980, 425) covers catalytic
hydrogenation, hydride substitution, metal/acid and metal/ammonia
reductions, halogen radical abstraction and sundry other reactions.
S.Krishnamurthy and H.C.Brown .J( Org. Chem., 1976, 41, 3064; 1980, 45, 849)
have made an interesting comparison of some of the hydride reagents used for
NS 2 substitution of Cl, ,rB I or OTs. These reagents are essentially based on the
tetrahydroborate or tetrahydroaluminate anions with many substituted variants
(see also R.C.Wade, .J Mol. Catal., 1983,18, 273). The best of these hydrides is
undoubtedly LiBHEt 3 which has much better nucleophilicity than LiAIH 4
(S.Krishnamurthy and H.C.Brown, .J Org. Chem., 1983, 48, 3085) and readily
reduces hindered alkyl halides and mesylates (R.W.Holder and M.G.Matturro,
.J Org. Chem., 1977, 42, 2166). This reaction is also effective with LiH and only a
catalytic amount of .B3tE
The use of polar solvents such as DMSO or sulpholane increases the
effectiveness of NaBH 4 as a reducing agent for tosylates (R.O.Hutehings et al.,
O.Jrg. Chem., 1978, 2259) 43, and (n-Bu4N)BH3CN is a particularly effective
reducing agent for derivatives of primary alcohols (R.O.Hutchings et al., .J Org.
Chem., 1977, 82). 42, Tertiary and benzylic alcohols have been reduced directly
with NaBH3CN/ZnI 2 by what appears to be a radical process (C.K.Lau et al.,
.J Org. Chem., 1986, ,15 3038).
Other new hydride reagents include KBHPh 3 (for primary bromides and
iodides only, N.M.Yoon and K.E.Kim, O.Jrg. Chem., 1987, ,25 5564) and
LiA1H(i-Bu)2(n-Bu) which is required in stoichiometric amount only rather than
the usual excess (S.Kim and K.H.Ahn, .J Org. Chem., 1984, 49, 1717). Zinc
borohydride shows high selectivity for hydride substitution in tertiary chlorides
without any competition from elimination (S.Kim, C.Y.Hong and S.Yang,
Angew. Chem., Int. Ed. Engl., 1983, 22, 562). This is the reverse of the normal
2NS selectivity for which primary iodides are the most reactive. The presence of
a catalytic amount of a transition metal salt can enhance the activity of 4 LiA1H
towards the reduction of alkyl halides and CoCl 2 andNiCl 2 are particularly
effective (J.O.Osby, S.W.Heinzmann and B.Ganem, .J Am. Chem. Soc., 1986,108,
67). E.C.Ashby and coworkers .J( Org. Chem., 1978, 43, 183) have taken this
approach one step further and investigated a series of lithium copper hydrides.
Quantitative reduction of Cl, Br, I and OTs at primary sitesi s achieved with
Li4CuH 5 in THF.
In situ formation of the iodide from primary and secondary alcohols with the
reagent Me3SiCI/NaI/MeCN followed by treatment with zinc and acetic acid is
a very convenient one-pot process for the reduction of alcohols (T.Morita,
Y.Okamoto and H.Sakurai, Synthesis, 1981, 32). This procedure will also reduce
simple ethers. Benzylic alcohols are converted to the hydrocarbon without the
reducing agent (T.Sakai et.al., Tetrahedron Lett., 1987, ,82 3817). Using a similar
strategy the reduction of tosylates by zinc and t-butanol can be achieved directly
in refluxing glyme if excess NaI is added (Y.Fujimoto and T.Tatsumo,
Tetrahedron Lett., 1976, 3325).
Hydride tranfer from Et3SiH to the stable carbocation generated v/a the
'protonation of a tertiary alcohol is a useful route to some hydrocarbons
(reviewed by D.N.Kursanov, Z.N.Parnes and N.M.Loim, Synthesis, 1974, 633).
When the carbocation is unstable ( with respect to rearrangement or elimination)
the protic acid can be replaced with advantage by FB 3 (M.G.Adlington,
M.Orfanopoulos and J.L.Fry, Tetrahedron Lett., 1976, 2955).
Deoxygenation of secondary alcohols is often particularly difficult by
procedures involving nucleophilic substitution and a radical process can be a
convenient alternative. The alcohol is suitably derivatised and then
decomposed in presence of a radical activator and hydrogen donor.
ROH r ROX r "R ~ RH
)3(
This type of reaction has been thoroughly reviewed by W.Hartwig
(Tetrahedron, 1983, 39, 2069) and since it is rarely applied to the formation of
hydrocarbons per se it will only be discussed briefly. The derivative )3( usually
contains a thiocarbonyl group since the sulphur atom is particularly sensitive to
radical attack and many different types have been investigated. The radical
reducing agent is usually (n-Bu)3SnH. The additional presence of triethylborane
promotes the reduction at 20~ (K.Nozaki, K.Oshima and K.Utimoto,
Tetrahedron Lett., 1988, 6125) 29, thus providing exceptionally mild conditions
for deoxygenation. The readily accessible acetates of secondary alcohols are
reduced by Ph3SiH with t-butylperoxide as initiator (H.Sano, M.Ogata and
T.Migita, Chem. Lett., 1986, 77). The silane )4( is found to be even more effective
since high yields are also obtained with primary and tertiary acetates (H.Sano,
T.Takeda and T.Migita, Chem. Lett., 1988, 119).
Ph2HSi-C6H4-SiHPh2 ROC--NC6HTT
I
)4( NHC6H11 )5(
An analogous catalytic reduction (Pd on carbon) of an N,N'-dicyclo-
hexylisourea )5( gives the hydrocarbon RH quantitatively (E.Vowinkel and
I.Biithe, Chem. Ber., 1974,107, 1353). Hydrogenation of alkyl halides with Na-K
alloya s catalyst is enhanced by the use of a phase transfer agent such as a crown
ether or tris(3,6-dioxaheptyl)amine (A.K.Bose and P.Mangiaracina, Tetrahedron
Lett., 1987, ,82 2503).
R'SH
RO2CCO 2 N RH
N
Refluxing C6H6
s//
)6(
A new procedure particularly suitable for tertiary alcohols involves formation
of an oxalate hydroxamic ester of type (6). Treatment with a suitable thiol results
in homolysis of the hydroxamic bond followed by expulsion of two moles of
CO 2 (D.H.R.Barton and D.Crich, .J Chem. Soc., Perkin Trans. ,1 1986, 1603). The
best thiol was Et3CSH which has a very low nucleophilicity. Hindered second-
ary and tertiary acetates are best reduced with Li/EtNH 2 or K/18-crown-6/t-
BuNH 2 (D.H.R.Barton and coworkers, .J Chem. Soc., Chem. Commun., 1978, 68).
(c) From thio- and seleno- compounds
The removal of sulphur from alkyl sulphides, sulphoxides or sulphones has
long been achieved by hydrogenation with Raney nickel. Recently Mo(CO) 6 in
acetic acid has been shown to be effective for desulphurization of thiols
(H.Alper and C.Blais, .J Chem. Soc., Chem. Commun., 1980, 169) and catalysis
by molybdenum compounds is likely to be increasingly important in this area.
Other long established but more specific methods of removing the sulphur atom
involve Li/EtNH 2 at low temperature or sodium amalgum in MeOH. The
activity of sodium amalgum is improved by buffering with Na2HPO 4
(B.M.Trost et al., Tetrahedron Lett., 1976, 3477). With Pd(Ph3P) 4 as catalyst
LiBHEt 3 is effective for the removal of ,S SO 2 and Se from unreactive sites
(R.O.Hutchins and K.Learn, O.Jrg. Chem., 1982, 4380) 47, and reductive
deselenization of phenyl selenides occurs quantitatively with NaBH4/NiC12
(T.G.Back et al., O.Jrg. Chem., 1988, ,35 3815) or with Ph3SnH in refluxing
toluene (D.L.J.Clive et al., .J Am. Chem. Soc., 1980,102, 4438).
(d) From carbonyl and carboxylic derivatives
The traditional methods of converting aldehydes and ketones to the
hydrocarbon require strongly acidic (Clemmenson reduction, reviewed by
E.Vedejs, Org. Reactions, 1975, ,22 401) or strongly basic conditions (Wolff-
Kishner reduction). These relatively harsh conditions are unsuitable to much of
modern Synthetic methodology and much milder procedures haveb een
