STUDY OF SOLVATION PHENOMENA OF SOME SIMPLE MOLECULES FROM MEASUREMENT OF THEIR DIPOLE MOMENTS; AMMONIA AND THE ETHYL-AMINES

71 Pages·02.266 MB·English

by  NAUGHTON, JOHN JOSEPH

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Xerox University Microfilms
300 North Zeeb Road
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LD3907 *1}^ | <i0 t> 3
. c-7 Naught on, John Joseph. 1 ' t
1942 Study of solvation phenomena of some
,N3 simple molecules from measurement of
their dipole moments; ammonia and the
ethyl amines... dlew Yorka 1942,
2p.l.,57 typewritten leaves, tables,
diagrs. 29cm.
Thesis (Ph.D.) - New York university,
Graduate school, 1942.
Bibliography: p .56-57.
A78258~
Xerox University Microfilms, Ann Arbor, Michigan 48106
THIS DISSERTATION HAS BEEN MICROFILMED EXACTLY AS RECEIVED.
STUDY OP SOLVATION PHENOMENA
OF SOME SIMPLE MOLECULES FROM
MEASUREMENT OF THEIR DIPOLE MOMENTS
-AMMONIA AND THE ETHYL AMINES
by
John J? Naughton
February 1942
A dissertation in the department
of Chemistry submitted to the faculty of
the Graduate School of Arts and Science
in partial fulfillment of the requirements
for the degree of Doctor of Philosophy.
ACKNOWLEDGEMENTS!
The writer wishes to express his
appreciation and sincerest thanks to
Dr. William West for his aid and guid­
ance in the execution of this work.
He also wishes to thank Dr. R.
Garmen for the design and for his aid
in the construction of the capacity
measurement instrument used.
TABLE OF CONTENTS
Sublect Page
Purpose of Research ---------— ------— — ------— —— 1
Historical Background of Work--------------------------------—— 2
General Theory ----------— — •------------------------------------- 4
Description of Apparatus and Method of Use -
1. For Ammonia-------------------------------. — 9
2. For Diethylamine and Triethylamine———- 14
5. For Ethyl amine--------------------------------------- 15
4. Dielectric Measuring Apparatus----- ------------ 16
Purification of Materials— -------—--------------------------—— 19
Calculation of Results—— -------------------------------------- 2J
Discussion of Errors— -----------------——------------- 27
Resul ts------------------------------------------------------------------------- -47
Discussion of Results--------------—— -----------------------—— 31
Summary of Results------------------------------------------------------ 55"
Bibliography---------------------------------------------------------------- S(>
PURPOSE OP THE RESEARCH»
It is the purpose of this thesis, and of the research that is
back of it, to investigate the possibilities of the use of
dielectric polarization measurements in the studies of molecular
association and solute-solvent interaction in solution*
The family of compounds used for these measurements, ammonia
and the amines, was chosen because of the wide scale of reactions
possible with these compounds, as judged from their structure and
from the reactions of similar compounds in the oxygen series. They
were also chosen because of the more definite possibility of inter­
pretation of the results in view of the more gradual gradation of
properties that should be observed in going from ammonia to
triethylamine, than, for example, in the case of the oxygen series
(water, ethyl alcohol and ether) already mentioned.
It might also be noted that the dielectric polarization study
of ammonia and the amines in solution has been somewhat neglected.
Ethylamine has never been measured in solution, to the best of the
w riter's knowledge.
The choice of solvents was such as to obtain some that were
non-reactive, to establish a norm for the substances being studied
in solution, and others that would react in a known way, as judged
by other evidence.
2.
HISTORICAL BACKGROUND OP WORKi
Tremendous research efforts have been expended on the study
of the anomalous behavior of certain molecules in solution, from
the earlier efforts at measurement of vapor pressure effects to
the present day work on such solutions with the infra red spectro­
graph.
The use of the dielectric apparatus as a tool for such research
has not been overlooked. Indeed a considerable amount of knowledge
has been gained of the association mechanism of solute molecules
from such studies. This work has been chiefly on halogenated
compounds, alcohols and carboxylic acids in non-polar solvents (1).
The normal dielectric behavior of solutions has been adequately
investigated by Muller (2).
The dieleotric polarization studies of anomalous mixtures are
based on the possibility of compound formation, at least of an
incipient sort. Whether this type of compound formation, between
apparently saturated molecules, is a result of van der Waals
forces, dipole-dipole association or formation of a definite
coordinate link, as is the most recent opinion (5) (4), remains to
be seen. Infra red studies seem to substantiate the view that, in
many cases, the anomaly observed is the result of molecular compound
formation through a coordinated hydrogen, or hydrogen bond.(5).
It is reasonable to suppose that, if compound formation
involves dipole association, the polarization of the mixture
would be less than the sum of the two separate values, whereas
the introduction of a coordinate link resulting from chemical
union, should result in definite exaltation of the polarization.
There seems to be some evidence from published work that suoh
increases do, in fact, occur where compound formation appears
probable (6) (7). This view was taken by Earp and GlasBtone (8)
and used in their study of solute-solvent complex formation in
such solutions as ether in the halogen methanes. This work was
amplified and extended by Hammick, Norris and Sutton (9)»
No measurements seem to have been made on systems involving
such simple and interesting molecules as water and ammonia, with
the view of interpreting the results along the lines just
mentioned. With such a point in mind, a series of runs to
measure the molecular polarization of ammonia in various solvents
was attempted. The results were at first inconclusive because of
lack of satisfactory means of interpretation. The story of the
successful method, and the results, are contained in the following
text.
Studies of the homologous series of ethyl amines was then
made. The results of such a series determination enables us to
te ll much about possible reactions giving anomalous results, and
about the mechanisms of the reactions involved.
GENERAL THEORYt
(Note - Most of the following general theory and description
of apparatus is extracted from the w riter's Masters
Thesis, "The Dipole Moment of Ammonia in Various
Solvents")
A molecule can be considered as made up of an unevenly
distributed conglomeration of positive and negative charges, these
being the nuclei and electrons of the constituent atoms. All of
these charges can be summed together and said to act at a point,
one for the positive and another for the negative charges, giving
us positive and negative centers analogous to centers of gravity.
If these centers coincide we have what is known as a "nom-polar"
molecule. If they do not coincide the molecule will act as a
small charged rod, one end positive and the other negative. The
magnitude of either of these charges, since they are equal, times
the distance between them is called the "dipole moment" of the
molecule.
CALCULATION OP THE DIPOLE MOMENT:
If a molecule contains a dipole and is placed in an electric
field it will try to orient itself in the field, positive pole to
negative plate and negative pole to positive plate. It will thus
have an effect on the chargee of the plates which is measured as
the dieleotric constant of the substance composed of the molecules,
and is, strictly, the ratio of the capacity of the plates with the
substance in question between them to the capacity of the plates
in vacuo.
It must be realized that the dielectric constant of a
substance is due to another factor besides the permanent dipole
of the molecules, for the field will move the charge centers,
inducing a dipole of its own. The value of this induced moment
will depend on many factors, among them the size of the charges,
the internuclear distances and the force constants of the bonds
between the atoms of the molecule. It is a constant for each molecule
and is known as its Polarisability, and is defined, as it is measured,
by the moment induced in the molecule by a field of unit strength
acting on it. The dielectric constant can then be set up as the sum
of two factors - permanent dipole and induced dipole.
Clausius and Mosotti gave us the equation relating dielectric
constant and induced dipole:
E - 1 . M _ 4wil <*;_ „
m T ’ 5 - p
where F s dielectric constant; M s molecular weight; d * density;
N ■ Avogadro's Number; P » molar Polarization; of,- Polarizability.
This is an equation that is true for a molecule of zero permanent
dipole, a molecule with symmetrically placed charges or atoms, i.e .,
a norwpolar molecule.