Analysis of Organoaluminium and Organozinc Compounds

364 Pages·1968·6.42 MB·English

by  T. R. Crompton, R. Belcher and H. Freiser (Auth.)

ANALYSIS OF ORGANOALUMINIUM
AND ORGANOZINC
COMPOUNDS
by
T. R. CROMPTON, B. Sc., F. R. I. C.
ÔÌßáíçÍ*· AWARD
TOINOMTNY 1···
PERGAMON PRESS
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Copyright © 1968
Pergamon Press Ltd.
First edition 1968
Library of Congress Catalog Card No. 67-31075
08 012578 6
This book is dedicated to
my Mother
and my Wife Elisabeth
PREFACE
UNTIL approximately fifteen years ago the organo compounds of aluminium
and zinc were regarded as chemical curiosities of no industrial importance.
However, over the past decade, due principally to the discoveries of Ziegler
and Natta, these compounds—particularly those of aluminium—have ac-
quired great importance in the chemical industry. Thus, in 1964 the world
production of polyethylene manufactured by the low pressure (including the
Phillips process) catalysed route exceeded 500 million lb, and has now risen
to approximately a third of the world production of polyethylene manu-
factured by the conventional high pressure process. Also, organoaluminium
compounds are becoming of increasing interest as intermediates in the
manufacture of organic chemicals. During this ten-year period, therefore,
there has developed the need for methods of analysing such compounds.
When the author first became interested in this problem some ten years
ago there existed few analytical methods in the literature and in most cases
it was necessary to work out a suitable procedure in the laboratory. Several of
these procedures have since been published. In the meantime other workers
have published their results of work carried out on the development of
analytical procedures. The author has kept closely in touch with these
developments and has tried out many of the published procedures, and where
possible has compared the results obtained between different methods. In
this book are discussed developments in the field of the analysis of organo-
aluminium and organozinc compounds covering the world literature up to
1964.
Organoaluminium and organozinc compounds, especially those of low
molecular weight, are spontaneously pyrophoric and must be handled in an
inert atmosphere with great care. Any degree of contamination of the
sample by air, moisture etc., during storage or handling involves the risk
either of a serious accident or of sample contamination with consequent in-
validation of the final analytical result. Techniques have been evolved for
handling these compounds safely and without the risk of partial decomposi-
tion. Chapters 1 to 3 discuss methods for the determination of various
functional groups and elements in organoaluminium compounds, viz. alkyl,
hydride, alkoxide, amino and thio alkoxide groups, also aluminium and
halogens. Using these methods it is possible to elucidate the empirical for-
mula of the sample and obtain information regarding the nature and amount
of functional groups present. In Chapters 4 and 5 are discussed various
solution methods of analysis of organoaluminium compounds including
xi
xii PREFACE
various titrimetric procedures (conductometric, potentiometric and di-
electric constant) and also methods based on spectrophotometry and lumo-
metry. In Chapter 6 is discussed an iodometric titration method for analysing
organoaluminium compounds. This method is particularly useful for rapid
analysis of diluted samples. Chapter 7 discusses recent extensive and pro-
mising work on the analysis of organoaluminium compounds by thermo-
metric titrimetry with suitable reagents. This procedure provides a rapid
analysis, and in favourable circumstances can distinguish between the various
components of a mixture. Purely analytical applications of infrared, Raman
and nuclear magnetic resonance spectroscopy to the analysis of organo-
aluminium compounds are at present somewhat limited. Nevertheless, these
techniques hold promise and are discussed in Chapter 8. Many of the methods
which have been devised for organoaluminium compounds are also applicable
with minor modifications to the analysis of organozinc compounds (Chap-
ter 9).
At the end of most Chapters is included a selection of detailed procedures
for carrying out various analyses. This is considered to be a particularly useful
feature of the book as most of these analyses have not been described in the
literature or are described in insufficient detail. Reference to a particular
instrument in these methods merely implies that this instrument was the one
available when the original work was carried out. There is no doubt that
alternate instruments could be used provided they meet the specifications
indicated in the method.
It is hoped that this book will be useful to workers in the field of analysis
of organoaluminium and organozinc compounds both in Industry and in
University and also to the student of analytical chemistry. Many of the
techniques that are appropriate to these types of compounds will also find
application in the analysis of other organometal compounds (e.g. thermo-
metric titration can be applied to the analysis of lithium alkyls). Consequently
workers in other fields may find much to interest them.
Ashton-on-Mersey,
T. R. CROMPTON
Cheshire, England
ACKNOWLEDGEMENTS
THE illustrations in this book, aside from those taken from the author's
personal files, are from a variety of sources. Reproduction of the following
illustrations and tables is authorized through the courtesy of the persons
and publications named herewith:
Analytical Chemistry, The American Chemical Society, 1155 Sixteenth
Street, N.W., Washington 6, D.C. (Figures 22, 23, 24, 70, 73, 74, 75, 76,
77, 99, Tables 35, 36, 61, 62, 64).
Journal of the American Chemical Society, The American Chemical Society,
address as above (Table 77).
Liebigs Annalen der Chemie, Verlag Chemie G.m.b.H., Pappelallee 3,
694 Weinheim an der Bergstrasse, Germany (Figures 68, 69, 78, 79, 80,
Table 60).
Zeitschrift für Analytische Chemie, Verlag Chemie G.m.b.H., address as
above (Figures 56, 57, 59, 60, 61, 62, 63).
Beckmann Instruments Inc., Scientific and Process Instruments Division,
Fullerton, California (Figure 72).
Bulletin. Sociιtι Chimique de France, Masson et Cie, 120, Boulevard Saint-
Germain, Paris VI (Figures 91, 92).
Canadian Journal of Chemistry, Division of Administration and Awards,
National Research Council, Ottawa 2, Ontario (Figure 90, Tables 78, 79).
Journal of Chemical Physics, The American Institute of Physics, 335 East
45th Street, New York 17, New York (Figure 89, Table 86).
Chemische Berichte, Verlag Chemie G.m.b.H., Pappelallee 3, 694 Weinheim
an der Bergstrasse, Germany (Figures 34, 35, 36, 37, 38, 39,40,41,42,44,45,
46, 65, 66, 67).
Chemica e Industria, Piazzale R, Morandi 2, Milan (Figures 54, 55).
Bulletin of the Chemical Society of Japan, 5, 1/Chome, Kanada/Surugadia,
Chiyoda Ku, Tokyo (Figures 101, 102, Tables 83, 84, 85).
Doklady Akad. Nauk SSSR, Izdatel'stvo Akademii Nauk SSSR, Pod-
sosenskii pen 21, Moscow B-62 (Figures 47, 48, 49).
Zeitschrift für Elektrochemie, Verlag Chemie G.m.b.H., Pappelallee 3,
694Weinheim an der Bergstrasse, Germany (Figures 93,94,95,96,97,98,104).
F and M Scientific Europa Ν. V., London W.3 (Figure 21).
Journal of Inorganic and Nuclear Chemistry, Pergamon Press Ltd., Heading-
ton Hill Hall, Oxford, England (Tables 80, 81, 82).
Établissements Jouan, 113 Boulevard Saint-Germain, Paris VI (Figure 28).
Elementary Practical Chemistry, Part III, Quantitative Organic Analysis,
xiii
xiv ACKNOWLEDGEMENTS
Á. I. Vogel (1958) (Figure 33). Longmans, Green and Co. Ltd., 48 Grosvenor
Street, London W.l.
Metal Alkoxides, Volume 23 in the Advances in Chemistry Series by D. C.
Bradley (1959), The American Chemical Society, 1155 Sixteenth St., N.W.,
Washington 6, D.C. (Reference 88).
Infrared and Raman Spectra of Polyatomic Molecules (page 419) by G.Herz-
berg, Copyright 1945, D. Van Nostrand Company, Inc., 120 Alexander Street,
Princeton, New Jersey (Reference 67).
Recuiel des Travaux Chimiques, Nederlandse Chemische Vereniging, Lange
Voorhoul 5, The Hague (Figure 103).
Organometallic Chemistry by K. Ziegler (1960), Reinhold Publishing Cor-
poration, 430 Park Avenue, New York 22, New York (Reference 43).
Journal of Physical Chemistry, The American Chemical Society, 1155 Six-
teenth St., N.W., Washington 6, D.C. (Figure 100).
Alkyls Bulletins, Triethylaluminium Analytical Methods Numbers Ô 68 5-4
and T68 5-5 (9th October 1959). Stauffer Chemical Company Speciality
Chemical Division, Exclusive Sales Agent, New York City, New York
(Figures 7, 16, 17, Reference 5).
Talanta, Pergamon Press Ltd., Headington Hill Hall, Oxford (Figures 71,
72, 81, Table 63).
Organometallic Compounds, 2nd Edition, G.E.COATES, J.Wiley and Sons
Ltd., 605, Third Avenue, New York 16, New York (Reference 96).
The author also gratefully wishes to acknowledge assistance from a num-
ber of colleagues. These include Mr. V. W.Reid who first introduced him to
the subject of analysing organoaluminium and organozinc compounds;
Dr. L.A.Goodson who carried out a very valuable literature search on the
subject matter of the book; Drs. W.L.Everson and Evelyn M.Ramirez of
Shell Development Co., Emeryville, California who provided the manu-
scripts for Chapters 7 and 9.5; Mr. L.W.Myers who prepared Chapter 2.2
on gas chromatographic methods of analysis. Thanks are also due to Mr. T. A.
Shaw and Mrs. J. Hamilton for processing the manuscript, to Mr. R. Moss
and others for their extensive services, to Mr. J. A. Brassell for preparing vari-
ous figures, and to Mrs. D. Crook and others for typing the manuscript.
The author also records his thanks to his wife Elisabeth for proof-reading.
Without such assistance the task of writing this book would have presented
many more difficulties.
CHAPTER 1
ANALYSIS OF ORGANOALUMINIUM COM-
POUNDS CONTAINING ALKYL AND
ALKOXIDE GROUPS UP TO BUTYL
AND HYDRIDE GROUPS
In a method described by Ziegler [1,2] for the determination of lower
alkyl and hydride groups in organoaluminium compounds, a known weight
of sample is reacted at a low temperature with 2-ethyl hexanol in a specially
constructed nitrogen- or helium-filled gasometric system. Upon alcoholysis,
each alkyl group liberates one mole of paraffin gas and each hydride group
liberates one mole of hydrogen as follows:
"AlCJHa.+i + HOCH - CH—CH CH -> "Al—OCH - CHCH CH + C„H
2 2 3 2 2 3 2ll2+
I I
C H5 C H5
2 2
"A1H + HOCH - CH—CH CH -> "Al—OCH - CHCH CH + H
2 2 3 2 2 3 2
I I
C2H5 Q2H5
The alkyl and hydride contents of the samples are then calculated from
the quantity of gas evolved from a known weight of sample and from the
composition of the gas withdrawn from the system at the end of the analysis.
Mass spectrometric and other methods of gas analysis are used for determin-
ing the composition of the evolved gas mixture.
Ziegler states [2] that gas recoveries obtained by his procedure were lower
than expected from the composition of the samples analysed. He attributed
the low gas yields to a partial solution of the evolved paraffin-hydrogen mix-
ture in the 2-ethyl hexanol reagent. Crompton and Reid [3] have tested this
procedure against pure redistilled samples of triethylaluminium and triiso-
butylaluminium and confirmed that lower than expected gas yields were
obtained when either 2-ethyl hexanol or n-hexanol were used as alcoholysis
reagents. It was evident, however, from their results that incomplete reaction
of alkyl and hydride groups with the alcoholic reagent was the principal cause
of the low gas recoveries obtained. Thus, appreciably higher gas yields were
1 TP
1
2 ORG ANO ALUMINI UM AND ORGANOZINC COMPOUNDS
NITROGEN
INLET
„ ZINC SULPHATE
"Π FILLED TORPEDO
FIG. 1. Apparatus used for alcoholysis-hydrolysis of organoaluminium
compounds.
ANALYSIS OF ALKYL AND ALKOXIDE GROUPS 3
obtained when sample decomposition was effected using a mixture of n-hexa-
nol and monothylene glycol or a mixture of water and monothylene glycol
than when 2-ethyl hexanol alone was used. Crompton and Reid studied the
reaction of lower alkyl groups (up to butyl) and hydride groups with a wide
range of hydroxylic compounds (alcohols, glycols, water) to find a suitable
reagent for the quantitative decomposition of each type of organoaluminium
compound.
Gas-liquid chromatography was considered to be a simple and rapid
method of analysing the mixture of paraffin, hydrogen and nitrogen with-
drawn from the gasometric apparatus after sample decomposition and this
method of gas analysis was used through the investigation. Work carried
out in developing methods for the determination of alkyl and hydride groups
in trimethylaluminium, triethylalummium, tri-n-propylaluminium and tri-
isobutylaluminium and some of their chloro and alkoxide derivatives is
discussed below. The detailed procedure is described in Method 1 at the end
of this Chapter.
The apparatus, which is similar to that described by Ziegler et al. [2], is
shown in Fig. 1. it consists of a reaction vessel attached by means of a flexible
coupling to a gas manifold system, incorporating a gas burette for volumetric
measurement of the gas evolved, and leads to a gas sampling torpedo for
transfer of the gas to the gas-liquid Chromatograph for subsequent analysis.
Mercury is used as the confining liquid in both the gas burette and the samp-
ling torpedo. The manifold system connects to a supply of pure nitrogen
which is dried by passage through a drying tower packed with Linde 4A
molecular sieve. The reaction vessel connects, via a stopcock, to a supply of
aqueous zinc sulphate solution, which is used for discharging the reaction
gases into the sampling torpedo. The interior of the apparatus should be
cleaned and dried thoroughly before each determination.
At the commencement of the determination the interior of the apparatus
is filled with dry and oxygen-free nitrogen. This prevents oxidation and/or
hydrolysis of alkyl and hydride groups in the sample by atmospheric oxygen
and moisture which, if it occurred, would cause low results to be obtained.
Contamination of the organoaluminium compound during transference
from the sample tube to the reaction vessel (Fig. 1) is prevented by surround-
ing the tip of the transfer pipette with a nitrogen-flushed T-piece (Fig. 2).
Smooth reaction between the reagent (contained in the rotatable side-
limb) and the organoaluminium compound is ensured by cooling the reac-
tion mixture to — 60 °C. The reaction vessel is then heated to 100 °C for
30 min, to complete the reaction, and, finally cooled to room temperature
and allowed to equilibrate before noting the volume of gas produced. The
mixture of nitrogen, paraffin(s) and hydrogen in the apparatus is then dis-
placed into a mercury-filled torpedo. Methods used to analyse these gas
mixtures by gas-liquid chromatography are summarized in Table 1 and are
described fully in Method 1 at the end of this Chapter.