Vibration fundamentals of cyclic difluorodiazirine compound from ultraviolet absorption spectru

Bartky, I. R.

Bass, A. M.

Simmons, J. D.

English

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NATIONAL BUREAU 
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8625 
VIBRATIONAL FUNDAMENTALS OF CF2N2 FROM THE 
ULTRAVIOLET ABSORPTION SPECTRUM ?I 
. +  d 
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Technical Report  
t o  
Nat ional  Aeronautics and Space Adminis t ra t ion 
Washington, D. C. 
U.S. DEPARTMENT OF COMMERCE 
, 
NATIONAL BUREAU OF STANDARDS 
https://ntrs.nasa.gov/search.jsp?R=19660010205 2020-03-16T23:19:21+00:00Z
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NATIONAL BUREAU OF STANDARDS REPORT 
NBS PROJECT NBS REPORT 
221-11-221OL61 February 1, 1965 8625 
by 
J. D. Simmons, I. R .  Bartky and A. M. Bass 
Techni C N ~  Report 
t o  
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Washington. D. C.  
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U. S. DEPARTMENT OF COMMERCE 
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Preface 
A manuscript  based upon t h i s  r e p o r t  w i l l  
be submitted for pub l i ca t ion  as a L e t t e r  t o  t h e  
Ed i to r  i n  t he  Journal  of Molecular Spectroscopy. 
VIBRATIONAL FUNDAMENTALS OF CF2N2 FROM THE 
ULTRAVIOLET ABSORP TI0 N S P E C T R U ~  
by 
J. D. Simmons'"', I .  R.  Bartky and A. M. Bass 
Abstract  
The u l t r a v i o l e t  absorp t ion  spec tn  "I qf CF,N, has been 
observed and found t o  inc lude  bands of  two types.  All of the  
bands of one type  can be analyzed i n  terms of fou r  t o t a l l y  
symmetric v i b r a t i o n a l  f requencies  p l u s  a prominent sequence 
o f  d i f f e r e n c e  bands. Some bands o f  the  second type can be 
i n t e r p r e t e d  as v i b r o n i c a l l y  allowed fundamentals induced by 
t h e  n o n t o t a l l y  symmetric t o r s iona l  v i b r a t i o n .  This l a t t e r  
assignment r e v e a l s  enough information t o  account for t h e  
d i f f e r e n c e  bands of t h e  f i rs t  type. All ground s t a t e  funda- 
mental  assignments a r e  compatible wi th  e a r l i e r  i n f r a r e d  and 
Raman r e s u l t s .  
_ _  
Work supported i n  p a r t  by t h e  National Aeronautics and Space 
Administrat , ion.  
... , . - r 
,< \L 
I\ ,\ 
Nat iona l  Academy of  Sciences-National Research Council 
Pos tdoc to ra l  Research Associate a t  t h e  Nat ional  Bureau 
o f  Standards.  
- 2 -  
CF,N2 has  r e c e n t l y  been prepared and c h a r a c t e r i z e d  by 
Mitsch (L). 
and i n t e r p r e t e d  i n  terms of  a c y c l i c  d i a z i r i n e  s t ruc ture  as 
opposed t o  the isomeric linear diazomethane structure (2). 
fo l lowing  pre l iminary  v i b r a t i o n a l  a n a l y s i s  of  t h e  e l e c t r o n i c  
spectrum i s  o f f e r e d  a s  f u r t h e r  support  f o r  t h a t  assignment. 
The i n f r a r e d  and Raman s p e c t r a  have been observed 
The 
The u l t r a v i o l e t  absorp t ion  spectrum has  been observed i n  
0 
t h e  3750-3000 A reg ion  under h igh  r e s o l u t i o n  and wi th  s u f f i c i e n t  
pa th- lengths ,  u s ing  a mul t ip l e  r e f l e c t i o n  c e l l ,  t o  observe t h e  
v i b r o n i c a l l y  allowed ground s t a t e  fundamentals. The system 
c o n t a i n s  bands o f  a t  l eas t  two d i s t i n c t  types ;  a s t rong  group 
o f  broad bands wi th  t h r e e  i n t e n s i t y  m a x i m a  and a much weaker 
group wi th  one prominent sharp  m a x i m u m .  
On t h e  b a s i s  o f  a c y c l i c  d i f l u o r o d i a z i r i n e  wi th  C2 sym- V 
met ry ,  t h e r e  a r e  f o u r  t o t a l l y  symmetric v i b r a t i o n s  of spec ie s  
A , ,  and f i v e  n o n t o i a l l y  symmetric v i b r a t i o n s  - one, two and 
i w v  vi' species  A, ,  E, tuiu u 2 ,  r e s p a ~ u v a ~ y .  v s u i v i i ~ ~  ac:lt;L- 
t i o n  rules a l low only  t o t a l l y  symmetric fundamental and combina- 
t i o n  f r equenc ie s  t o  appear  i n  t h e  e l e c t r o n i c  spectrum wi th  t h e  
same band-type as t h e  o r i g i n  band. 
fundamental  which appears  wi th  apprec iab le  i n t e n s i t y  due t o  
v i b r o n i c  i n t e r a c t i o n  must have a band-type d i f f e r e n t  from t h a t  
of t h e  o r i g i n .  
--J n - _ _ _ _ _ ~ z - - - i - -  ir:a.---: 
Any n o n t o t a l l y  symmetric 
All of t h e  broad-type bands can e a s i l y  be i n t e r p r e t e d  i n  
- ,3 - 
terms o f  four t o  t a l l y  symmetric v i b r a t i o n a l  f r equenc ie s  accom- 
panied by a s t r o n g  sequence o f  d i f f e r e n c e  bands wi th  t h e  o r i g i n  
a t  28374.6 cm'l. 
v i b r a t i o n s  i s  summarized i n  Table  I where t h e  r e s u l t s  from t h e  
u l t r a v i o l e t  d a t a  are  compared with those  from Ref. 2. The 
agreement f o r  %he ground s t a t e  fundamentals i s  ve ry  good except  
f o r  vg.  Here,  a l though t h e  dev ia t ion  between t h e  i n f r a r e d  and 
t h e  u l t r a v i o l e t  d a t a  i s  uncomfortably l a r g e ,  t h e  assignment i n  
each case  i s  r a t h e r  convincing. 
The assignment f o r  t hese  t o t a l l y  symmetric 
The r e l a t i v e  i n t e n s i t i e s  o f  t h e  upper s t a t e  p rogres s ions ,  
i n  dec reas ing  o r d e r ,  a r e  v1 ( 4  members), vq ( 2  members) , vg 
(1 member) and v,. 
appears  i n  t h e  long-path experiments,  i t  has much less i n t e n s i t y  
than  does vl, even though i t  has a more f avorab le  Boltzmann 
d i s t r i b u t i o n .  
and i s  presumably overlapped by s t ronge r  bands i n  the  expected 
While the  ground s t a t e  v2 fundamental 
The v, upper s t a t e  fundamental i s  n o t  observed 
r e g i n n -  Since v1 and \J mzy he dPSCrihed as the  sp-metr ic  NN 4 
s t r e t c h  and symmetric CF, deformation r e s p e c t i v e l y ,  one would 
conclude from Franck-Condon cons idera t ions  t h a t  t h e  most s i g n i f -  
i c a n t  change i n  geometry between t h e  two e l e c t r o n i c  states i s  a 
s t r e t c h i n g  of  t h e  ni t rogen-ni t rogen bond which expands t h e  r i n g  
and e f f e c t s  some change i n  t h e  FCF angle .  
It  should also be noted t h a t  t h e  n o n t o t a l l y  symmetric vg 
t o r s i o n a l  v i b r a t i o n  ( spec ie s  A z )  which has  a Raman a c t i v e  
. - 4 -  
i'requency of 451 cm-l (2) also appears i n  t h e  e l e c t r o n i c  spectrum 
by vi i i ron ic  i n t e r a c t i o n .  As expected from t h e  s e l e c t i o n  r u l e s ,  
t n r  ground and upper s ta te  fundamentals -- with  f r equenc ie s  Of  
u 8  cm" and 327 cm'l, r e s p e c t i v e l y ,  from t h e  broad-type o r i g i n  -- 
are bands o f  the  sharp type.  
n convincing assignment f o r  t h e  above mentioned s t rong  sequence 
of oroad-type d i f f e r e n c e  bands which has a 120.6 cm'l i n t e r v a l .  
T h i s  low frequency v i b r a t i o n  o f f e r s  
The vg assignment does not,, however, account  f o r  all of  t h e  
sha rp  bands observed. There i s  pre l iminary  evidence f o r  another  
t r a n s i t i o n  i n  t h i s  region.  
P rogres s  inc lud ing  an a t tempt  t o  ana lyze  t h e  p a r t i a l l y  reso lved  
r o t a t i o n a l  s t r u c t u r e  by an asymmetric r o t o r  contour  technique.  
Fur ther  work on t h i s  system i s  i n  
The au tho r s  are g r a t e f u l  t o  3r. Ronald Mitsch of  t h e  Minne- 
s o t a  Mining and Manufacturing Company f o r  supplying t h e  sample and 
t o  D r .  Norman Craig f o r  making a p r e p r i n t  o f  R e f .  2 available i n  
advance of  pub l i ca t ion .  
- 5 -  
REFERENCES 
(1). Ronald A .  Mitsch, J. Heterocycl ic  Chem. 1, 59 (1964). 
(2). C. W. Bjork,  N. C. Craig, R. A .  Mitsch and J. Overend, 
J. Am. Chem. SOC. (in p r e s s ) .  
- 6 -  
Table I. V i b r a t i o n a l  Assignment f o r  t h e  4 Species  i n  CF2N2 
U l t r a v i o l e t  (vapor)  
I R  (vapor)  Raman (liq.1 This work 
V l b r u  LI on R e f .  2 Ror. 2 VI! V '  
( cm-1)  ( cm-1)  ( cm-1) ( cm-1) 
V1 1563 1560 1564.0 1436 9 
v2 
v3 805 804 775 0 643.3 
1282 1280 1282.9 ---- 
v4 502 500 500.2 516.0 


Vibrational Fundamentals of CF2N2 from the Ultraviolet Absorption Spectrum

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