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Xerox University Microfilms
300 North Zoeb Road
Ann Arbor, Michigan 48106
1103907 i3^nflfcX
. G7 Kay, W illiam Lewis, 1916- 1 ' 11
1942 The photolysis of dim ethyIhydrazine
.K3 " . . . New York, 1942.
2 p .l.,4 6 typ ew ritten leaves. ta b le s,
d iag rs. 29cm.
Thesis (Ph.D.) - New York u n iv e rs ity ,
Graduate school, 1942.
B ibliography: p .45-46.
AQ4708
c
Shelf List
Xerox University Microfilms, Ann Arbor, Michigan 48106
THIS DISSERTATION HAS BEEN MICROFILMED EXACTLY AS RECEIVED.
The Photolysi3 of Dim ethylhydrazine
A Thesis
Subm itted in P a rtia l F u lfillm en t of the
Requirements fo r the
Degree of Doctor of Philosophy
at
New York U niversity
fcy
^
o-A x
William L* Kay
March 1942
Index
Introduction Page 1
C h em icals Page 6
Apparatus . . . . . . Page 9
Experimental P ro c e d u re Page 15
Data and B e su lts Page 22
D is c u s s io n Page 38
Summary Page 44
B ib lio g ra p h y Page 45
Acknowledgement
The author wishes to express his
ap preciatio n to Professor H.A. Taylor the
d irec to r of th is research. He also wishes
to express h is ap p reciatio n to Dr. M ilton
Burton fo r h i3 help fu l comments. L astly , he
wishes to thank the Physics Department of
New York U niversity fo r th e use of the
spectrographie equipment.
Introduction (l a »t »c »)
A photochemical reactio n takes place as a consequence
of the absorption of lig h t. During the prim ary process
the absorbing molecule e ith er d isso ciates or is brought
to a s ta te such th a t i t s energy has been augmented by
th at of the quantum absorbed. The secondary reactio n s
include a l l those processes which the products of
d isso c ia tio n or the excited m olecules e ith e r undergo or
in it i a t e .
The prim ary photochemical process may be defined a3
the act of absorption of a quantum, to g eth er with the
events which may happen to an energy-rich molecule up
to and including reactio n or d isso c iatio n .
In general term s, i f a molecule A absorbs a quantum
of energy su ffic ie n t to in itia te a photochemical rea ctio n ,
(A-*«2*A') , th e subsequent p o s s ib ilitie s may be w ritte n :
Nature of Process ----- R epresentative R eaction
I. Fluorescence A1 —>A
I I . D eactivation by A’ 4-M — *- A-f- M
c o llisio n s or w alls
I I I . D irect or spontaneous A '—»D]_* Dg+-
D issociation
IV. D isso ciatio n induced A’-t-M —* D-^ +’ Dg+--+M
by c o llisio n s or by
external fie ld s
V. In te rn a l rearrangem ent A1—>B
or isom erization
VI. R eactions with other A' + B —»C + -----
m olecules.
A' rep resen ts an upper s ta te , stab le or u n stab le, of the
absorbing m olecule. M rep resen ts e ith e r another m olecule
in the homogeneous phase, the surface of the reactio n
v e sse l, or an external fie ld . To th ese p o s s ib ilitie s may be
added those of in te rn a l reo rg an izatio n or degradation of
the absorbed energy which rep resen ts a sp ecial case of
p o s s ib ility II; and in gases at high x>ressures, recomb
in a tio n of the products of d isso c iatio n .
Spectroscopy o ffe rs one of the most im portant roads
to the u ltim ate understanding of the prim ary process. If ther*
is sharp abso rp tio n , the l if e of the a ctiv a ted s ta te w ill
be long and i t would be expected th at the molecule would
change to stab le m olecules, lose i t s energy by c o llis io n
with other m olecules or emit i t s energy as lig h t. This
la s t phenomenon is fluorescence.
If th ere is a broadness of the lin e s in a spectrum,
the lif e of the upx>er sta te is g en erally not as long as
with sharp absorption. In some cases, a magnetic f ie ld
w ill increase the broadness of the lin e s. The presence of
other m olecules, by pressure increase, v;ill do the same
th in g. Tfifs^sfior?ening of the l if e of the upper s ta te is
termed induced p re d isso c ia tio n in d istin c tio n to p re
d isso c ia tio n i t s e l f which is caused when the upper s ta te
movWs1 to11 ano s ta te in a time of more than one
v ib ra tio n period.
Sometimes in a spectrum the bands of d isc re te absorp
tio n move clo ser and closer to g eth er and are followed by
a region in which absorption is continuous. In the excited
s ta te s , th e re fo re , the v ib ra tio n a l and ro ta tio n a l lev e ls
now no longer e x is t. F ra n ck ^ ^ sta te d th a t in th is region
of continuous absorption the molecule has d isso ciated into
fragm ents, which can be atoms, m olecules or ra d ic a ls.
This i n i t i a l step is very rap id , taking place in le ss than
one v ib ratio n period; hence, the h a lf l i f e of the upper
s ta te must be very short.
The continuum may be only an experim ental one i f the
ro ta tio n a l s ta te s are so close together as to make the
lin e s unresolvable by ordinary o p tic a l means. If the begin
ning of the continuum is d iffu se , the h a lf l i f e of the
upper sta te is probably short. The short l if e might s ta r t
v/ithin the continuum and escape n o tice.
i ° 1
Franck ; made a most h elp fu l co n trib u tio n to the
study of sp ectra when he explained the observation th a t a
molecule may absorb q u a n titie s of energy larg e r than the
energy of d isso c ia tio n and s t i l l not be destroyed, by
showing th a t in such cases not a ll of the absorbed energy
is av ailab le as v ib ra tio n a l energy. Instead a larg e part
of the absorbed energy is consumed in raising the electron
system to a higher quantum state, the remaining energy
being available only for changing the vibrational and
rotational states.
The photochemical decomposition of hydrazine has
been studied by several investigators, but no work has
been reported on symmetrical dimethylhydrazine. The spectrum
of hydrazine ( S ) shows faint diffuse bands, (apparently
predissociation bands) beginning at about 2490.2 in 80 cm.
layers of vapor at 0.5 mm.. pressure. Continuous absorption
begins at about 2370A. Hilgendorff^ ^ gives the heat of
dissociation as 122.4 k. cal./m ol. (only an approximation)
There is no general agreement as to the secondary
reactions in hydrazine decomposition, but the primary
rupture has been fa irly well established as
The presence of atomic hydrogen has been established by
(5)
Bamford by photolysis of hydrazine in the presence of
propylene.
In the gaseous state, methylamine exhibits a series
of diffuse predissociation absorption bands beginning at
2440.2, which increase in in tensity toward the shorter
wave-lengths. This is attributed to an electronic excitation
in the amino grou^ Bneleus and J o lle y ^ state that methyl
amine, on exposure to ligh t from a mercury arc or an
aluminum spark, produces equal amounts of ammonia and
hydrogen plus a liq u id , with sm aller q u a n titie s of methane
and n itro g en . The prim ary rea ctio n is believed to form
('fc)
C%NH and H, rath e r than CH3 and NHg*
West^7f has studied the Banian spectrum of symmetrical
dim ethylhydrazine and fin d s i t to be, lik e th a t of hydrazine,
c h a ra c te ris tic of an asymmetric m olecule. In the Baman
spectrum th ere are no strong lin e s except those corresponding
-1 -1
to C-H and W-H v ib ratio n s around £900 cm. and 3300 cm. ,
re sp e c tiv e ly , and in p a rtic u la r th ere are no strong lin e s
of about 1000 c m . i n the p o sitio n to be expected i f the
two halves of the molecule could exercise a symmetrical
v ib ra tio n with respect to one another. Two weaker lin e s of
1010 cm. “I and 1118 cm. -1 seem to be comparable with the
p a ir a t 904 cm."1 and 1117 cm.-1 of hydrazine in aqueous
a ttrib u te d
so lu tio n , of which one or o th er, or both, are * e ss e n tia lly
to the N-PT v ib ra tio n , while the lin e a t 475 cm. is
probably causec£*Vthe corresponding bending vibration.tChe
follow ing is W est's favored stru c tu re fo r dim ethylhydrazine
seen "end-on".
CH
5.
