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Ultraviolet and infrared absorption spectra of 2-thiophenesulfonamides
SpectrochimicaActa, Vol. 30A, pp. 611 to 618. PergamonPress 1974. Printed in Northern Ireland
Ultraviolet and int,ared absorption spectra of 2-thiophenesulfonamides ANTONINO I~kRCORIA, E~ANUELE MACCARONE,
GIUSEPPE I~IusuMARRA a n d GAETANO A. TOM~SEL~ Istituto di Chimica Industriale dell' Universit~ V. ]e A. Doria 8, 95125 Catania--Italy (Received 4 June 1973)
Absiracf~--The uv and ir absorption spectra of thirty-one 2-thiophenesnlfonamides have been investigated. The uv spectroscopic data are discussed in relation to the absorption of some parent compounds and the spectral changes are correlated with substituent effects. The ir stretching frequencies of N - - H bond are reported. In KBr discs, only one N - - H stretching absorption band, due to associated sulfonamide, is observed. In CCI4 solutions, however, two bands, due to free and associated N - - H group, are present. A good correlation is found between the H a m m e t t substituent constants and the N - - H frequencies. Also, the ir stretching of S--O, C---S and S---N bonds is briefly discussed. II~TRODUCTIOI~ FOLLOWING w o r k on t h e r e a c t i v i t y a n d t h e spectroscopic b e h a v i o u r of s o m e t h i o p h e n e d e r i v a t i v e s [1], in this p a p e r t h e u v a n d ir s p e c t r a o f 2 - t h i o p h e n e s u l f o n a m i d e s listed in T a b l e 1 are r e p o r t e d . T h e u v s p e c t r a o f b e n z e n e s u l f o n a m i d e s h a d b e e n i n v e s t i g a t e d in relation t o t h e i r biological a c t i v i t y [2], b u t no s t u d y on 2 - t h i o p h e n e s u l f o n a m i d e s h a s b e e n carried out. I n this w o r k we i n t e r p r e t t h e u v spectroscopic b e h a v i o u r b y t h e e v a l u a t i o n of t h e c h r o m o p h o r e s responsible for t h e a b s o r p t i o n a n d discuss t h e a s s i g n m e n t o f t h e m a i n ir s t r e t c h i n g frequencies o f N - - H , S - - O , C - - S bonds. EXPERIMENTAL
Syntheses T h e c o m p o u n d s u s e d in this s t u d y were s y n t h e s i z e d b y a d d i n g 2-thiophenes u l p h o n y l chloride (0.03 mole) in m e t h a n o l t o a solution o f a m i n e (0.06 mole) in m e t h a n o l . T h e r e a c t i o n w a s k e p t until c o m p l e t i o n b y boiling t h e m i x t u r e for t h r e e hours, t h e n m e t h a n o l was e v a p o r a t e d a n d t h e residue was t r e a t e d w i t h cold a q u e o u s 40 ~o s o d i u m h y d r o x i d e a n d e x t r a c t e d twice w i t h e t h e r or filtered. T h e a q u e o u s l a y e r was acidified a n d t h e p r e c i p i t a t e filtered off, w a s h e d a n d crystallized several t i m e s f r o m a q u e o u s ethanol. [1] A. ARCORXA,E. MACOA~ON~.,G. MUSUMAm~ and G. TOUaSELLI, J . Org. Chem., 38, 2457 (1973); G. A_LBERGHI~A,A. ARCORIA, S. FISICBELLAand G. SCA~LATA,Spectrochim. Acta 38A, 2063 (1972); A. A~CORIA, •. lV~CCAROI~-E,G. I~USUMARRA and G. RO~A~o, ibid. 29A, 161 (1973); A. A R c e d , E. MACC~RO~E and G. TO~A~ELLI, ibid. ~gA, 1601 (1973). [2] W. D. Ku~T.~R and L. A. STRUT, J . AM. Chem. Soc. 65, 2349 (1943); P. H. BELL, J. F. BO~rE and R. O. RoBIa~, JR., ib/d. 66, 847 (1944); L. DOUB and J. M. VA-~-I)ENBELT,ibid. 69, 2714 (1947); 71, 2414 (1949); R . J . W . CR~.MT.Y~,T.PRIcE-Jo~u~sandF.J. SwI~mou~E J . ffhem. Soc. (C), 1738 (1968). 611
612
A. ARCO~A, E. M~CCA~O~E, G. M u s ~ a m ~ Table
1. P h y s i c a l
constants
and G. Tomau~LI~
of 2-thiophenesulfonamides Analysis C(%)
SOr--X M.p.(°C)
X= 1 NH s 2 NH--CH a 3 N(CHs) 5 4 NH C6H s 5 NH---CeH4CH 3 6 NH---CeHaCH s 7 NH--CsH4CH s 8 NH---CeH4OCHs 9 NH---CeH4OCH8 10 l~IH---CeH4OCH 8 11 N H - - - C e H a O H 12 N H - - - C e H 4 O t t 13 : N H - - - C e H a O H 14 I~IH---C6H4C1 15 N H - - C e H a C 1 16 N H - - C 6 H 4 C 1 17 N H - - - C e H a N O ~ 18 N H - - C e H 4 N O ~ 19 N H - - C 6 H ~ N O s 20 N H - - G e H a C ~ H s 21 N H - - C e H a C z H ~ 22 N H - - C ~ H a C ~ H ~ ~ 23 I~H--C~H~CaH~ i 24 I~H---C~Ha(CHs) z 25 ~ H - - C ~ H a ( C ~ H a ) ~ 26 N H CeYIa(C~H~) ~ i 27 ~ H - - n a p h t h y l 28 N H - - n a p h t h y l 29 N H - - - p y r i d i l 30 l ~ l H - - p y r i d i l 31 l ~ H - - p y r i d i l
2' 3' 4' 2' 3' 4' 2' 3' 4' 2' 3' 4' 2' 3' 4' 2' 4' 2' 4' 2', 6' 2', 6 ' 2', 6 ' ~ fl ~ fl y
147 71-2 79 99--100 138 88-9 115 86 72-3 104 144-5 152 135 117 114 115 104-5 162-3 165 76 61-2 124 97 173 117 162 178 125 215 188-9 300
Formula
Found
. . . . CoHlaNO~S 2 . . CxxHnNO~S ~ . . . . C,1HnNOaS 2 . . . . CxoHoNOsS2 CloHoNOsS2 CIoHgNOsSs CloHsC1NOsSs . . . . C,oHeN~O~S ~ C~oHsN~O4Sz . . C,zI-IxsNO2S ~ C~H~NO~S~ C~aHI~NOsS s C~sH16NO~S ~ Cx~HxaNO~S ~ C1~H17NO2S ~ C,~H~aNO~S ~ C~4Ha,I~O~S ~ C14HIlNO~S ~ C~HsN~O~S ~ CoHoNaO~Sa G~HsN~O~S ~
. . 46.68 . 51-95 . . 48"88 . . 46.92 46.95 46'98 43.54 . . 42"29 42-28 . 53.84 53.81 55.56 55"60 53'78 57"03 59'36 57-99 58.04 45"08 45.10 45.12
Calc. . . 46"73 . 52.15 . . 49.06 . . 47.05 47.05 47"05 43.88 . . 42.25 42.25 . 53.91 53.91 55-49 55"49 53"91 56.92 59.41 58.11 58.11 44"99 44"99 44-99
H(%) Found
Calc.
. .
. . 5.57
.
. 4"25
. .
. . 3"99
. .
. . 3'60 3.63 3"61 2"86
. .
. . 2"86 2"89
.
. 4'98 4'92 5"45 5'43 4-86 5.88 6.47 3.77 3"81 3"42 3-38 3-33
N(%)
. . 5.66 . 4.38 . . 4.12 . . 3"55 3.55 3.55 2"95 . . 2-84 2.84 . 4.90 4"90 5"37 5"37 4-90 5.80 6.54 3.83 3.83 3"36 3.36 3.36
Found
Calc.
Ref.
5.98
6.95
5.48
5.53
5.16
5"20
5.58 5.38 5.42 5"23
5.49 5.49 5-49 5.12
9.93 9"92
9.85 9"85
5.15 5-28 5"03 5"06 5"16 4-69 4.29 4.88 4.76 11'53 11.58 11.62
5.24 5.24 4.98 4'98 5"24 4.74 4'33 4.84 4.84 11-66 11-66 11.66
a b c d c e o c e e c c c o e o
c c f o c o
c c o c c o c c o
(a) H . D . HA~TOUOH, Thiophene and it~ Derivatives, p. 426. I n t e r s c i e n c e , N e w Y o r k (1952) (b) W . STEINKOPF a n d T. HOPI~ER, A n n . 501, 174 (1933). (e) T h i s w o r k . (d) A. P . TERElCT'EV a n d G. ]~!¢I.KADATSKII, Zh~r. Obohch. Khim. 22, 153 (1952); Chem. Abstr. 46, 11178 (1952). (e) A. A~CO~La, E . MACC~aONE, G. MUSU~ARRA a n d G. TO~ASELLI, J. Org. Chem,, 88, 2457 (1973). (f) S. OCE~IPINTI, G. SCAB~ATA a n d M. TORR:E, Boll. ~e~. Ace. Gioienia Sci. Nat. (Gatania), IV, 11, 181 (1973).
Ultraviolet spectra The ultraviolet spectra were obtained by standard methods with a HitachiPerkin-Elmer mod.EPS 3T spectrometer. The solutions, in 95~o ethanol, were a b o u t 10 -5 M.
Infrared spectra The infrared spectra of 2-thiophenesulfonamides were recorded in K B r discs and CC14 solutions using a 1 mm cell on a Perkin-Elmer model 237 spectrometer. RESULTS
AND
])ISCUSSIOI~
Ultraviolet spectra Table 2 lists the 2m~x and log e values of 2-thiophenesulfonamides here investigated; the inflections are indicated in parentheses. The spectrum of 2-thiophenesulfonamide (Fig. 1) showing a band at 238 nm (log e = 3.86) and an inflection at 250 n m (log e = 3.73), closely resembles t h a t of
Ultraviolet and infrared absorption spectra of 2-thiophenesulfonamides
613
T a b l e 2. U l t r a v i o l e t s p e c t r a o f 2 - t h i o p h e n e s u l f o n a m i d e s
~,max
log ~
X = --NH l ~4~802.--X
~'~
238 (250)
2' 3 ' y SO2NH-~4' Y~H CH s 0CH 8 OH C1 NO z
C2I-I5 C3H~ i
~ ~'~
~ SO~NH
~max
239 (250)
227 (250) 227 244 228 (250) (285) 227 (250) 283 (227) (240) 223 (240) 342
4-08 3.92 3.92 3.92 4-09 3.85 3.56 4.05 3.87 3.61 4-05 3.97 4"23 4-19 3.43
3.92 3.84
243 (255) 243 (253)
3.92 3"88 3-95 3"90
229 (250) 227 (250) (280) 227 (250) (280) 233 (255) 226 (255) (320)
log e
--N~
3.96
241 (255)
3'
3-87 4'
4"07 3'87 4"10 3.90 3-60 4.07 3.87 3.57 4.21 3.99 4"25 4.16 3"20
229 (250) 232 (250)
4.13 3-90 4.22 3.90
232 (252) (280) 233 (255) 231 (255) 313 375 229 (250)
4.18 3.87 3-52 4-19 3.98 4.10 3-91 4.01 3.60 4-19 3.97 4.15 3.92
229 (250)
Y ~ CH 8
C~H~
CsH? i
245 (255)
3"95 3'91
243 (255)
3"93 3'89
244 (255)
3"93 3"89
223 (260) 285
4"80 3"85 3-84
243 318
4"18 3"77
243 (260) (270) (280) (290) (315) 247 (305)
4.74 4.09 3.99 3.89 3.74 3.06 4-10 2"20
251 294
4.09 4.18
~ S02NH
log e
pNHCH~
2'
-S02NH2 2 B , ~
Y
3.86 3-73
~max
2-thienylmethyl sulfone [3]. This behaviour could be ascribed to the thiophenesulfonyl system excitation, determined by the conjugation between the thiophene ring and the sulfonyl group (I).
[3] S. G~ONOWITZ, Advances in Heterocyvlic Chemistry, Vol. 1 (A. R . KATRZ~ZK~ E d ) , p. 17. A c a d e m i c P r e s s . , N e w Y o r k (1963}.
614
A. ARCORIA,E. MACCSLRO~rE,G. MUSU~A~Aand G. TOMAS~.I~Z
4-0
- j~
~ .
g
G%.
2
°
,
,
300
.
.
.
...... .
250
X,
.
.
.
.
.
.
.
.
350
nnl
Fig. 1. Ultraviolet spectra of some 2-thiophenesulfonamides. A similar absorption curve is observed for N-methyl and pyperidine compounds. l~or N-phenyl derivatives instead, besides the chromophore (I), the absorption due to the N-phenyl conjugation (II), which increases the intensity of the band at higher frequencies (Fig. 1), is observed. II The compounds containing --CH 3, ---OCH3, ---OH and --C1 groups, in the 3' and 4' positions of the benzene ring, give spectra not remarkably different from that of 2-thiophenesulfonanilide, except an inflection at about 280 nm present in the ---OCH a and - - O H derivatives. I n the spectra of 2' substituted sulfonamides, instead, the intensities of the band at higher frequencies are lower than those of 3' and 4' isomers probably because the steric hindrance between the substituent and the NH group decreases the conjugation with the aromatic ring. This effect is remarkable in 2'-ethyl, 2'-isopropyl and 2',6'-disubstituted derivatives, whose spectra are similar to that of N-methyl-2thiophenesulfonamide (Fig. 1). The presence of a nitro group in the benzene ring always determines a noteworthy change in the absorption spectra in comparison with the unsubstituted compound, showing a wide absorption band towards red, due, for 2'- and 4'-nitro isomers~ to the nitro-aniline conjugation (Fig. 2). The spectra of ~ and ~ naphthalene derivatives are characterized by a high absorption band at 223-228 nm, due mainly to the naphthylamlne chromophore, and
Ultraviolet and infrared absorption spectra of 2-thiophenesulfonamides
615
"'",,.
"
"\.\.
.o
2'-NO
2 ,
3'-NO 2 . . . . . . 4'-NO
i
i
i
i
\
'\
2 ..........
I i 25o
",,
~
i
,
=
l
3oo
,
f
L
i
3~0
~
\ t
~
,
I
400
v
~
,
T
I
45o
X, nm Fig. 2. U l t r a v i o l e t spectra o f 2-tbiophene-nltro-mllfonamides.
b y a succession of inflections in the range 260-315 nm ascribed to the fine structure of the monosubstituted naphthalene ring system [4]. The spectroscopic behaviour of 2-thiophenesulfonamidopyridines is also interesting. The absorption curves of ~ and F derivatives (Fig. 3), point out the presence in solution of imino-forms (III) and (IV), as for other snlfonamidopyridines [5].
III
I H
IV
The ~ isomer, instead, exists predominantly in the sulfonamido-form. Infrared spectra
I n Table 3 are provided the ir stretching frequencies, in K B r discs, of the N - - H , S--O, G--S and S - - N bonds. In 2-thiophenesulfonamide the N H 2 stretching is splitted into two bands located at 3320 and 3240 cm -1, ascribed respectively to the asymmetric and symmetric stretching vibrations of the primary amino group [6]. I n the secondary sulfonamidcs only one band of strong intensity is observed and its position (3200-3275 cm -1) [4] A. ETIEN~rE and B. RU'XIM:EYER,Bull. Soc. Ohim. France ~.,3, 1588 (1953); H. BABAand S. Suzts~t Bull. Soy. Ghim. Japan, 84, 82 (1961). [5] R. A. JON~S and A. R. KAz~-Tz3rr, J. Ghem. ~qoc. 378 (1961); T. A. MAST~U-XOVA,Y~r. N. S H ~ r ~ R , I. K. KUZNETSOVA,E. M. PERESLENI,T. B. SA~r~A~OVAandM. l. ~:A~ACm~-~, Tetrahedro~, 19, 357 (1963). [6] M. ST. C. FLm~, Sl~ctrochim. Acta 18, 1537 (1962).
616
A. ARCOBIA,E. MACCARON~,G. M U S ~
and G. TOI~ASELLI
Table 3. Ir stretching frequencies of 2-thiophenesulfonamides N--H X = 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29
30 31
S02
SOr--X
iNrHa * lffI-I C H a N(CH2) 5 NH C6H 5 NH--C~HaCH a NH--CeH4CH 8 NH--C6H4CH 3 NH---CeHaOCH a N~C6Ha0Ctt a NH----CeHaOCH a NH----CsH4OH NH--C~I-I40I~I I ~ H - - - C aI-I40 I-I NH--CaHaCI NH--CeH4C1 NH--CeH4CI NH--CeH4N0 ~ l g I-I---C 6I-I41~TO 2 N H - - C 6I-Ial~TO2 !gH---C6HaC2H 5 NH--CeH4CzH 5 I~TH--C6HaCaI-I7 i I~H--C6H~CaH 7 i NH--CsHa(CHa) 2 NH--C~I~a(C2H~) 2 N I ~ - - - C 6 H a ( C a H T ) $'/ IqH--naphthyl NH--naphthyl NH--pyridil l~H--pyridil NI-I--pyridil
3320L3240 s 3275 s -3210s 3 2 0 0s 32458 3235s 3265a 3250$ 3265s 3205s 3245a 3 2 6 0s 3 2 6 0s 3235s 32358 3270s 3255s 3330s 3220s 3 2 1 0s 3265s 3260s 3 3 0 0s 3275s 3 2 6 0s 3215s 3250s 3240w 3260w 3220w
2' 3' 4" 2' 3' 4t 2' 3~ 4' 2' 3' 4' 2' 3' 4' 2' 4' 2' 4' 2', 6' 2', 6' 2', 6' ~ ~ ~ ~ ~'
asym.
sym.
2325 s 1325s 1333s 1335s 1330s 1330s 1 3 4 0s 1345s 1335s 1335s 1 3 3 0s 1 3 5 0s 1 3 3 5n 1340s 1330s 1 3 3 0s 1 3 5 5s 1335s 1340s 1328s 1335s 1335s 1348s 1 3 3 0s 1 3 4 0s 1 3 4 0s 1342a 1352s 1 3 5 6s 1356s 1 3 3 0s
1155s ll60 s 1160s 1145s 1 1 5 0s 1153s 1160s 1 1 6 0s 1150s 1155s 1150s 1155s 1160s 1155s 1160s 1155s 1155s 1145s 1160s 1155s 1155s 1155s 1153s 1153s 1152s 1155s 11585 1150s 1133s 1 1 5 0s 1 1 3 0s
* T h e s p e c t r u m is c o i a c i d e n t t o t h a t r e p o r t e d b y A . B u z A s a n d J . T E S T E ,
Cth--8
S--N
1100 w 1090 m 1098w 1092 m 1090 m 1093 m 1093w 1090 m 1099 m 1100 m 1090 m 1090 m 1096w 1092 w 1093m 1092m 1095w 1093 m 1090 m 1086 m 1088 m 1085ra 1089w 1090 m 1090 m 1095 m 1093w 1093 m 1088m 1095 m 1082 m
892 m 835s 925s 925s 915 m 920 m 910s 920s 895 s 905 m 920 m 883 m 890 m 910s 910a 912 m 915s 890s 915s 920 m 910 m 920 m 922 s 9 0 0s 905s 915 s 925 m 920 m 967 m 930~ 946s
Bull. Boc. Ohim. France 2 7 , 7 9 3 ( 1 9 6 0 ) .
4.0
w .
3.5
\,\i
\
3.0
i
I
i
i
I,
i
l
250
,
I 300
i
,
,
,
t
,
350
~., n m
Fig.
3.
Ultraviolet spectra of 2-thiophenesulfnamidopyridines.
Ultraviolet and infrared absorption spectra of 2-thiophenesulfonamides
617
gives evidence for the presence of the sulfonamide in the associated-form [7]. The spectra measured in carbon tetrachloride solutions (Table 4), instead, show two bands ascribed to the monomer N H (VNHmo,. ~- 3343 ± 23 cm -1) and to associated N H (VNHa~. ~ 3250 -}- 15 cm-1). This behaviour is similar to that of benzenesulfonamides, which are strongly associated in solution owing to intermolecular hydrogen bonds between N H and the sulfonyl oxygen [7]. Figure 4, where are reported VN~mo,. and VNHas~.against H a m m e t t ~ for 3' and 4' substituted 2-thiophenesulfonanilides, points out the correlation between the absorption frequencies and the substituent in the aromatic ring. 2' Substituted sulfonanilides, instead, are weakly associated even in saturated solution of carbon tetrachloride, as it results from the comparison between the T a b l e 4. S t r e t c h i n g f r e q u e n c i e s
X ~ lq CH a CI-I 3 CH a OCI-I 3 OCH a OCtt a C1 C1 C1 NO~. NO 2 NO 2
2' 3' 4' 2' 3' 4' 2' 3' 4' 2' 3' 4'
(era -1) o f N H
bond
i n CC14
free N H
associated NH
aHammet t
3366 3379 3369 3372 3350 3363 3374 3348 3361 3361 3286 3344 3326
3255 3270 3260 3260 3255 3255 3265 3260 3245 3245 -3235 --
O'0 --0-069 --0-17 0.11 --0"268 0.373 0"227 0"71 1"27
3400
NH o
3300
Assoclated
I
0"0
I
I
0"5
Hammett,
NH
I'0
¢,
Fig. 4. C o r r e l a t i o n b e t w e e n N H s t r e t c h i n g f r e q u e n c i e s a n d H a r n m e t t s u b s t i t u e n t constants. [7] R . KO~-IG a n d O.
I~AT/R-WS]~I,ibid., ~,.A, 219 (1968).
618
A. ARCORIA, E. MACCAROI'r~,G. MUSVMARRAand G. TOMASEL~
i n t e n s i t y b a n d o f t h e m o n o m e r sulfonanilide a n d t h a t of the associated one. This weak association could be explained as due to an intramoleeular chelation b e t w e e n t h e N H group a n d t h e s u b s t i t u e n t (OCHs, C1 a n d NO~) in the ortho position. Therefore the absorption frequencies of these sulfonanilides are lower t h a n those of 3' a n d 4' isomers, in a g r e e m e n t with t h e presence o f an i n t r a m o l e e u l a r h y d r o g e n b o n d [8]. I n fact, in the 2 ' - m e t h y l derivative, where no internal chelation is possible, n o f r e q u e n c y lowering with respect to 3' and 4' isomers is observed. The stretching v i b r a t i o n of t h e sulfonyl b o n d is splitted into t w o components, a s y m m e t r i c and s y m m e t r i c [9]. T h e assignment of these bands has been m a d e b y m a n y a u t h o r s for benzenesulfonamides and benzenesulfonanilides [10]. I n 2thiophenesulfonanilides the SO S a s y m m e t r i c stretching frequencies are located in the range 1355-1325 cm -1 a n d the s y m m e t r i c a l ones in t h e range 1160-1145 cm -1, according to l i t e r a t u r e data. T h e b a n d a t 904-4-11 cm -1, present in all the i n v e s t i g a t e d 2-thiophenesulfonamides, can be ascribed to t h e v i b r a t i o n Cth.--S, analogously t o Cbonz--S, which always occurs at a b o u t 1090 cm -1 [11]. T h e b a n d a t 904 d= 11 cm -1, due t o the S - - N b o n d stretching v i b r a t i o n [12], is i n d e p e n d e n t from the s u b s t i t u e n t in the aniline, as f o u n d for t h e benzene derivatives [13]. I n particular, in N - m e t h y l - 2 - t h i o p h e n e s u l f o n a m i d e this b a n d is located at 835 em -1, as in N - m e t h y l - p - t o l u e n s u l f o n a m i d e [14]. Moreover in ~ a n d 7 pyridine derivatives t h e S - - N stretching v i b r a t i o n a l mode is p r o b a b l y a t 946-967 cm-~; its position could be different from t h a t f o u n d for the o t h e r 2-thiophenesulfonamides because of the imino s t r u c t u r e of the nitrogen atom. Acknowledgements.---The authors are grateful to the Consiglio Nazionale delle Ricerche (Rome)
for financial support. [8] L. S. FERGUSON, The modern Structural Theory of Organic Chemistry, p. 527. Prentice-Hall, Englewood Cliffs, New Jersey (1964). [9] L. J. BEI~AWIY, The Infrared Spectra of Complex Molecules, 2 ed, p. 357. Wiley, New York, (1958). [10] S. DETO~ and D. H.'~DzI,Spectrochim. Acta 9, 601 (1957); E. A. ROBINSON, Can. J. Chem. 39, 247 (1961); A. E. LUTSKI and I. K. Is~rcRENXO, Zh. Obshch. Khim. 38, 1618 (1968); Chem. Abstr. 69, 95730 (1968). [11] T. UNo, K. MACmDA and K. H~-~AI, Spe~troehim. Acta 24~k, 1705 (1968); N. S. HAM, A. lV[. H_~)~BLYand R. H. L~BY, Aust. J. Chem. 13, 443 (1960). [12] A. R. KATRrrz~Y and R. A. JONES, J. Chem. Soc. 4497 (1960); G. V ~ s ~ v ~ , Vibrational Spectra of Benzene Derivatives, p. 391. Academic Press, New York (1969). [13] V. L. LEVAS~OVAand N. P. Lus~rI~A, Zh. Prikl. Spe]ctrosb. 10, 502 (1969); Chem. Abstr. 70, 119753 (1969). [14] D. H~I)Zi, J. Chem. Soc. 847 (1957).
Ultraviolet and int,ared absorption spectra of 2-thiophenesulfonamides ANTONINO I~kRCORIA, E~ANUELE MACCARONE,
GIUSEPPE I~IusuMARRA a n d GAETANO A. TOM~SEL~ Istituto di Chimica Industriale dell' Universit~ V. ]e A. Doria 8, 95125 Catania--Italy (Received 4 June 1973)
Absiracf~--The uv and ir absorption spectra of thirty-one 2-thiophenesnlfonamides have been investigated. The uv spectroscopic data are discussed in relation to the absorption of some parent compounds and the spectral changes are correlated with substituent effects. The ir stretching frequencies of N - - H bond are reported. In KBr discs, only one N - - H stretching absorption band, due to associated sulfonamide, is observed. In CCI4 solutions, however, two bands, due to free and associated N - - H group, are present. A good correlation is found between the H a m m e t t substituent constants and the N - - H frequencies. Also, the ir stretching of S--O, C---S and S---N bonds is briefly discussed. II~TRODUCTIOI~ FOLLOWING w o r k on t h e r e a c t i v i t y a n d t h e spectroscopic b e h a v i o u r of s o m e t h i o p h e n e d e r i v a t i v e s [1], in this p a p e r t h e u v a n d ir s p e c t r a o f 2 - t h i o p h e n e s u l f o n a m i d e s listed in T a b l e 1 are r e p o r t e d . T h e u v s p e c t r a o f b e n z e n e s u l f o n a m i d e s h a d b e e n i n v e s t i g a t e d in relation t o t h e i r biological a c t i v i t y [2], b u t no s t u d y on 2 - t h i o p h e n e s u l f o n a m i d e s h a s b e e n carried out. I n this w o r k we i n t e r p r e t t h e u v spectroscopic b e h a v i o u r b y t h e e v a l u a t i o n of t h e c h r o m o p h o r e s responsible for t h e a b s o r p t i o n a n d discuss t h e a s s i g n m e n t o f t h e m a i n ir s t r e t c h i n g frequencies o f N - - H , S - - O , C - - S bonds. EXPERIMENTAL
Syntheses T h e c o m p o u n d s u s e d in this s t u d y were s y n t h e s i z e d b y a d d i n g 2-thiophenes u l p h o n y l chloride (0.03 mole) in m e t h a n o l t o a solution o f a m i n e (0.06 mole) in m e t h a n o l . T h e r e a c t i o n w a s k e p t until c o m p l e t i o n b y boiling t h e m i x t u r e for t h r e e hours, t h e n m e t h a n o l was e v a p o r a t e d a n d t h e residue was t r e a t e d w i t h cold a q u e o u s 40 ~o s o d i u m h y d r o x i d e a n d e x t r a c t e d twice w i t h e t h e r or filtered. T h e a q u e o u s l a y e r was acidified a n d t h e p r e c i p i t a t e filtered off, w a s h e d a n d crystallized several t i m e s f r o m a q u e o u s ethanol. [1] A. ARCORXA,E. MACOA~ON~.,G. MUSUMAm~ and G. TOUaSELLI, J . Org. Chem., 38, 2457 (1973); G. A_LBERGHI~A,A. ARCORIA, S. FISICBELLAand G. SCA~LATA,Spectrochim. Acta 38A, 2063 (1972); A. A~CORIA, •. lV~CCAROI~-E,G. I~USUMARRA and G. RO~A~o, ibid. 29A, 161 (1973); A. A R c e d , E. MACC~RO~E and G. TO~A~ELLI, ibid. ~gA, 1601 (1973). [2] W. D. Ku~T.~R and L. A. STRUT, J . AM. Chem. Soc. 65, 2349 (1943); P. H. BELL, J. F. BO~rE and R. O. RoBIa~, JR., ib/d. 66, 847 (1944); L. DOUB and J. M. VA-~-I)ENBELT,ibid. 69, 2714 (1947); 71, 2414 (1949); R . J . W . CR~.MT.Y~,T.PRIcE-Jo~u~sandF.J. SwI~mou~E J . ffhem. Soc. (C), 1738 (1968). 611
612
A. ARCO~A, E. M~CCA~O~E, G. M u s ~ a m ~ Table
1. P h y s i c a l
constants
and G. Tomau~LI~
of 2-thiophenesulfonamides Analysis C(%)
SOr--X M.p.(°C)
X= 1 NH s 2 NH--CH a 3 N(CHs) 5 4 NH C6H s 5 NH---CeH4CH 3 6 NH---CeHaCH s 7 NH--CsH4CH s 8 NH---CeH4OCHs 9 NH---CeH4OCH8 10 l~IH---CeH4OCH 8 11 N H - - - C e H a O H 12 N H - - - C e H 4 O t t 13 : N H - - - C e H a O H 14 I~IH---C6H4C1 15 N H - - C e H a C 1 16 N H - - C 6 H 4 C 1 17 N H - - - C e H a N O ~ 18 N H - - C e H 4 N O ~ 19 N H - - C 6 H ~ N O s 20 N H - - G e H a C ~ H s 21 N H - - C e H a C z H ~ 22 N H - - C ~ H a C ~ H ~ ~ 23 I~H--C~H~CaH~ i 24 I~H---C~Ha(CHs) z 25 ~ H - - C ~ H a ( C ~ H a ) ~ 26 N H CeYIa(C~H~) ~ i 27 ~ H - - n a p h t h y l 28 N H - - n a p h t h y l 29 N H - - - p y r i d i l 30 l ~ l H - - p y r i d i l 31 l ~ H - - p y r i d i l
2' 3' 4' 2' 3' 4' 2' 3' 4' 2' 3' 4' 2' 3' 4' 2' 4' 2' 4' 2', 6' 2', 6 ' 2', 6 ' ~ fl ~ fl y
147 71-2 79 99--100 138 88-9 115 86 72-3 104 144-5 152 135 117 114 115 104-5 162-3 165 76 61-2 124 97 173 117 162 178 125 215 188-9 300
Formula
Found
. . . . CoHlaNO~S 2 . . CxxHnNO~S ~ . . . . C,1HnNOaS 2 . . . . CxoHoNOsS2 CloHoNOsS2 CIoHgNOsSs CloHsC1NOsSs . . . . C,oHeN~O~S ~ C~oHsN~O4Sz . . C,zI-IxsNO2S ~ C~H~NO~S~ C~aHI~NOsS s C~sH16NO~S ~ Cx~HxaNO~S ~ C1~H17NO2S ~ C,~H~aNO~S ~ C~4Ha,I~O~S ~ C14HIlNO~S ~ C~HsN~O~S ~ CoHoNaO~Sa G~HsN~O~S ~
. . 46.68 . 51-95 . . 48"88 . . 46.92 46.95 46'98 43.54 . . 42"29 42-28 . 53.84 53.81 55.56 55"60 53'78 57"03 59'36 57-99 58.04 45"08 45.10 45.12
Calc. . . 46"73 . 52.15 . . 49.06 . . 47.05 47.05 47"05 43.88 . . 42.25 42.25 . 53.91 53.91 55-49 55"49 53"91 56.92 59.41 58.11 58.11 44"99 44"99 44-99
H(%) Found
Calc.
. .
. . 5.57
.
. 4"25
. .
. . 3"99
. .
. . 3'60 3.63 3"61 2"86
. .
. . 2"86 2"89
.
. 4'98 4'92 5"45 5'43 4-86 5.88 6.47 3.77 3"81 3"42 3-38 3-33
N(%)
. . 5.66 . 4.38 . . 4.12 . . 3"55 3.55 3.55 2"95 . . 2-84 2.84 . 4.90 4"90 5"37 5"37 4-90 5.80 6.54 3.83 3.83 3"36 3.36 3.36
Found
Calc.
Ref.
5.98
6.95
5.48
5.53
5.16
5"20
5.58 5.38 5.42 5"23
5.49 5.49 5-49 5.12
9.93 9"92
9.85 9"85
5.15 5-28 5"03 5"06 5"16 4-69 4.29 4.88 4.76 11'53 11.58 11.62
5.24 5.24 4.98 4'98 5"24 4.74 4'33 4.84 4.84 11-66 11-66 11.66
a b c d c e o c e e c c c o e o
c c f o c o
c c o c c o c c o
(a) H . D . HA~TOUOH, Thiophene and it~ Derivatives, p. 426. I n t e r s c i e n c e , N e w Y o r k (1952) (b) W . STEINKOPF a n d T. HOPI~ER, A n n . 501, 174 (1933). (e) T h i s w o r k . (d) A. P . TERElCT'EV a n d G. ]~!¢I.KADATSKII, Zh~r. Obohch. Khim. 22, 153 (1952); Chem. Abstr. 46, 11178 (1952). (e) A. A~CO~La, E . MACC~aONE, G. MUSU~ARRA a n d G. TO~ASELLI, J. Org. Chem,, 88, 2457 (1973). (f) S. OCE~IPINTI, G. SCAB~ATA a n d M. TORR:E, Boll. ~e~. Ace. Gioienia Sci. Nat. (Gatania), IV, 11, 181 (1973).
Ultraviolet spectra The ultraviolet spectra were obtained by standard methods with a HitachiPerkin-Elmer mod.EPS 3T spectrometer. The solutions, in 95~o ethanol, were a b o u t 10 -5 M.
Infrared spectra The infrared spectra of 2-thiophenesulfonamides were recorded in K B r discs and CC14 solutions using a 1 mm cell on a Perkin-Elmer model 237 spectrometer. RESULTS
AND
])ISCUSSIOI~
Ultraviolet spectra Table 2 lists the 2m~x and log e values of 2-thiophenesulfonamides here investigated; the inflections are indicated in parentheses. The spectrum of 2-thiophenesulfonamide (Fig. 1) showing a band at 238 nm (log e = 3.86) and an inflection at 250 n m (log e = 3.73), closely resembles t h a t of
Ultraviolet and infrared absorption spectra of 2-thiophenesulfonamides
613
T a b l e 2. U l t r a v i o l e t s p e c t r a o f 2 - t h i o p h e n e s u l f o n a m i d e s
~,max
log ~
X = --NH l ~4~802.--X
~'~
238 (250)
2' 3 ' y SO2NH-~4' Y~H CH s 0CH 8 OH C1 NO z
C2I-I5 C3H~ i
~ ~'~
~ SO~NH
~max
239 (250)
227 (250) 227 244 228 (250) (285) 227 (250) 283 (227) (240) 223 (240) 342
4-08 3.92 3.92 3.92 4-09 3.85 3.56 4.05 3.87 3.61 4-05 3.97 4"23 4-19 3.43
3.92 3.84
243 (255) 243 (253)
3.92 3"88 3-95 3"90
229 (250) 227 (250) (280) 227 (250) (280) 233 (255) 226 (255) (320)
log e
--N~
3.96
241 (255)
3'
3-87 4'
4"07 3'87 4"10 3.90 3-60 4.07 3.87 3.57 4.21 3.99 4"25 4.16 3"20
229 (250) 232 (250)
4.13 3-90 4.22 3.90
232 (252) (280) 233 (255) 231 (255) 313 375 229 (250)
4.18 3.87 3-52 4-19 3.98 4.10 3-91 4.01 3.60 4-19 3.97 4.15 3.92
229 (250)
Y ~ CH 8
C~H~
CsH? i
245 (255)
3"95 3'91
243 (255)
3"93 3'89
244 (255)
3"93 3"89
223 (260) 285
4"80 3"85 3-84
243 318
4"18 3"77
243 (260) (270) (280) (290) (315) 247 (305)
4.74 4.09 3.99 3.89 3.74 3.06 4-10 2"20
251 294
4.09 4.18
~ S02NH
log e
pNHCH~
2'
-S02NH2 2 B , ~
Y
3.86 3-73
~max
2-thienylmethyl sulfone [3]. This behaviour could be ascribed to the thiophenesulfonyl system excitation, determined by the conjugation between the thiophene ring and the sulfonyl group (I).
[3] S. G~ONOWITZ, Advances in Heterocyvlic Chemistry, Vol. 1 (A. R . KATRZ~ZK~ E d ) , p. 17. A c a d e m i c P r e s s . , N e w Y o r k (1963}.
614
A. ARCORIA,E. MACCSLRO~rE,G. MUSU~A~Aand G. TOMAS~.I~Z
4-0
- j~
~ .
g
G%.
2
°
,
,
300
.
.
.
...... .
250
X,
.
.
.
.
.
.
.
.
350
nnl
Fig. 1. Ultraviolet spectra of some 2-thiophenesulfonamides. A similar absorption curve is observed for N-methyl and pyperidine compounds. l~or N-phenyl derivatives instead, besides the chromophore (I), the absorption due to the N-phenyl conjugation (II), which increases the intensity of the band at higher frequencies (Fig. 1), is observed. II The compounds containing --CH 3, ---OCH3, ---OH and --C1 groups, in the 3' and 4' positions of the benzene ring, give spectra not remarkably different from that of 2-thiophenesulfonanilide, except an inflection at about 280 nm present in the ---OCH a and - - O H derivatives. I n the spectra of 2' substituted sulfonamides, instead, the intensities of the band at higher frequencies are lower than those of 3' and 4' isomers probably because the steric hindrance between the substituent and the NH group decreases the conjugation with the aromatic ring. This effect is remarkable in 2'-ethyl, 2'-isopropyl and 2',6'-disubstituted derivatives, whose spectra are similar to that of N-methyl-2thiophenesulfonamide (Fig. 1). The presence of a nitro group in the benzene ring always determines a noteworthy change in the absorption spectra in comparison with the unsubstituted compound, showing a wide absorption band towards red, due, for 2'- and 4'-nitro isomers~ to the nitro-aniline conjugation (Fig. 2). The spectra of ~ and ~ naphthalene derivatives are characterized by a high absorption band at 223-228 nm, due mainly to the naphthylamlne chromophore, and
Ultraviolet and infrared absorption spectra of 2-thiophenesulfonamides
615
"'",,.
"
"\.\.
.o
2'-NO
2 ,
3'-NO 2 . . . . . . 4'-NO
i
i
i
i
\
'\
2 ..........
I i 25o
",,
~
i
,
=
l
3oo
,
f
L
i
3~0
~
\ t
~
,
I
400
v
~
,
T
I
45o
X, nm Fig. 2. U l t r a v i o l e t spectra o f 2-tbiophene-nltro-mllfonamides.
b y a succession of inflections in the range 260-315 nm ascribed to the fine structure of the monosubstituted naphthalene ring system [4]. The spectroscopic behaviour of 2-thiophenesulfonamidopyridines is also interesting. The absorption curves of ~ and F derivatives (Fig. 3), point out the presence in solution of imino-forms (III) and (IV), as for other snlfonamidopyridines [5].
III
I H
IV
The ~ isomer, instead, exists predominantly in the sulfonamido-form. Infrared spectra
I n Table 3 are provided the ir stretching frequencies, in K B r discs, of the N - - H , S--O, G--S and S - - N bonds. In 2-thiophenesulfonamide the N H 2 stretching is splitted into two bands located at 3320 and 3240 cm -1, ascribed respectively to the asymmetric and symmetric stretching vibrations of the primary amino group [6]. I n the secondary sulfonamidcs only one band of strong intensity is observed and its position (3200-3275 cm -1) [4] A. ETIEN~rE and B. RU'XIM:EYER,Bull. Soc. Ohim. France ~.,3, 1588 (1953); H. BABAand S. Suzts~t Bull. Soy. Ghim. Japan, 84, 82 (1961). [5] R. A. JON~S and A. R. KAz~-Tz3rr, J. Ghem. ~qoc. 378 (1961); T. A. MAST~U-XOVA,Y~r. N. S H ~ r ~ R , I. K. KUZNETSOVA,E. M. PERESLENI,T. B. SA~r~A~OVAandM. l. ~:A~ACm~-~, Tetrahedro~, 19, 357 (1963). [6] M. ST. C. FLm~, Sl~ctrochim. Acta 18, 1537 (1962).
616
A. ARCOBIA,E. MACCARON~,G. M U S ~
and G. TOI~ASELLI
Table 3. Ir stretching frequencies of 2-thiophenesulfonamides N--H X = 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29
30 31
S02
SOr--X
iNrHa * lffI-I C H a N(CH2) 5 NH C6H 5 NH--C~HaCH a NH--CeH4CH 8 NH--C6H4CH 3 NH---CeHaOCH a N~C6Ha0Ctt a NH----CeHaOCH a NH----CsH4OH NH--C~I-I40I~I I ~ H - - - C aI-I40 I-I NH--CaHaCI NH--CeH4C1 NH--CeH4CI NH--CeH4N0 ~ l g I-I---C 6I-I41~TO 2 N H - - C 6I-Ial~TO2 !gH---C6HaC2H 5 NH--CeH4CzH 5 I~TH--C6HaCaI-I7 i I~H--C6H~CaH 7 i NH--CsHa(CHa) 2 NH--C~I~a(C2H~) 2 N I ~ - - - C 6 H a ( C a H T ) $'/ IqH--naphthyl NH--naphthyl NH--pyridil l~H--pyridil NI-I--pyridil
3320L3240 s 3275 s -3210s 3 2 0 0s 32458 3235s 3265a 3250$ 3265s 3205s 3245a 3 2 6 0s 3 2 6 0s 3235s 32358 3270s 3255s 3330s 3220s 3 2 1 0s 3265s 3260s 3 3 0 0s 3275s 3 2 6 0s 3215s 3250s 3240w 3260w 3220w
2' 3' 4" 2' 3' 4t 2' 3~ 4' 2' 3' 4' 2' 3' 4' 2' 4' 2' 4' 2', 6' 2', 6' 2', 6' ~ ~ ~ ~ ~'
asym.
sym.
2325 s 1325s 1333s 1335s 1330s 1330s 1 3 4 0s 1345s 1335s 1335s 1 3 3 0s 1 3 5 0s 1 3 3 5n 1340s 1330s 1 3 3 0s 1 3 5 5s 1335s 1340s 1328s 1335s 1335s 1348s 1 3 3 0s 1 3 4 0s 1 3 4 0s 1342a 1352s 1 3 5 6s 1356s 1 3 3 0s
1155s ll60 s 1160s 1145s 1 1 5 0s 1153s 1160s 1 1 6 0s 1150s 1155s 1150s 1155s 1160s 1155s 1160s 1155s 1155s 1145s 1160s 1155s 1155s 1155s 1153s 1153s 1152s 1155s 11585 1150s 1133s 1 1 5 0s 1 1 3 0s
* T h e s p e c t r u m is c o i a c i d e n t t o t h a t r e p o r t e d b y A . B u z A s a n d J . T E S T E ,
Cth--8
S--N
1100 w 1090 m 1098w 1092 m 1090 m 1093 m 1093w 1090 m 1099 m 1100 m 1090 m 1090 m 1096w 1092 w 1093m 1092m 1095w 1093 m 1090 m 1086 m 1088 m 1085ra 1089w 1090 m 1090 m 1095 m 1093w 1093 m 1088m 1095 m 1082 m
892 m 835s 925s 925s 915 m 920 m 910s 920s 895 s 905 m 920 m 883 m 890 m 910s 910a 912 m 915s 890s 915s 920 m 910 m 920 m 922 s 9 0 0s 905s 915 s 925 m 920 m 967 m 930~ 946s
Bull. Boc. Ohim. France 2 7 , 7 9 3 ( 1 9 6 0 ) .
4.0
w .
3.5
\,\i
\
3.0
i
I
i
i
I,
i
l
250
,
I 300
i
,
,
,
t
,
350
~., n m
Fig.
3.
Ultraviolet spectra of 2-thiophenesulfnamidopyridines.
Ultraviolet and infrared absorption spectra of 2-thiophenesulfonamides
617
gives evidence for the presence of the sulfonamide in the associated-form [7]. The spectra measured in carbon tetrachloride solutions (Table 4), instead, show two bands ascribed to the monomer N H (VNHmo,. ~- 3343 ± 23 cm -1) and to associated N H (VNHa~. ~ 3250 -}- 15 cm-1). This behaviour is similar to that of benzenesulfonamides, which are strongly associated in solution owing to intermolecular hydrogen bonds between N H and the sulfonyl oxygen [7]. Figure 4, where are reported VN~mo,. and VNHas~.against H a m m e t t ~ for 3' and 4' substituted 2-thiophenesulfonanilides, points out the correlation between the absorption frequencies and the substituent in the aromatic ring. 2' Substituted sulfonanilides, instead, are weakly associated even in saturated solution of carbon tetrachloride, as it results from the comparison between the T a b l e 4. S t r e t c h i n g f r e q u e n c i e s
X ~ lq CH a CI-I 3 CH a OCI-I 3 OCH a OCtt a C1 C1 C1 NO~. NO 2 NO 2
2' 3' 4' 2' 3' 4' 2' 3' 4' 2' 3' 4'
(era -1) o f N H
bond
i n CC14
free N H
associated NH
aHammet t
3366 3379 3369 3372 3350 3363 3374 3348 3361 3361 3286 3344 3326
3255 3270 3260 3260 3255 3255 3265 3260 3245 3245 -3235 --
O'0 --0-069 --0-17 0.11 --0"268 0.373 0"227 0"71 1"27
3400
NH o
3300
Assoclated
I
0"0
I
I
0"5
Hammett,
NH
I'0
¢,
Fig. 4. C o r r e l a t i o n b e t w e e n N H s t r e t c h i n g f r e q u e n c i e s a n d H a r n m e t t s u b s t i t u e n t constants. [7] R . KO~-IG a n d O.
I~AT/R-WS]~I,ibid., ~,.A, 219 (1968).
618
A. ARCORIA, E. MACCAROI'r~,G. MUSVMARRAand G. TOMASEL~
i n t e n s i t y b a n d o f t h e m o n o m e r sulfonanilide a n d t h a t of the associated one. This weak association could be explained as due to an intramoleeular chelation b e t w e e n t h e N H group a n d t h e s u b s t i t u e n t (OCHs, C1 a n d NO~) in the ortho position. Therefore the absorption frequencies of these sulfonanilides are lower t h a n those of 3' a n d 4' isomers, in a g r e e m e n t with t h e presence o f an i n t r a m o l e e u l a r h y d r o g e n b o n d [8]. I n fact, in the 2 ' - m e t h y l derivative, where no internal chelation is possible, n o f r e q u e n c y lowering with respect to 3' and 4' isomers is observed. The stretching v i b r a t i o n of t h e sulfonyl b o n d is splitted into t w o components, a s y m m e t r i c and s y m m e t r i c [9]. T h e assignment of these bands has been m a d e b y m a n y a u t h o r s for benzenesulfonamides and benzenesulfonanilides [10]. I n 2thiophenesulfonanilides the SO S a s y m m e t r i c stretching frequencies are located in the range 1355-1325 cm -1 a n d the s y m m e t r i c a l ones in t h e range 1160-1145 cm -1, according to l i t e r a t u r e data. T h e b a n d a t 904-4-11 cm -1, present in all the i n v e s t i g a t e d 2-thiophenesulfonamides, can be ascribed to t h e v i b r a t i o n Cth.--S, analogously t o Cbonz--S, which always occurs at a b o u t 1090 cm -1 [11]. T h e b a n d a t 904 d= 11 cm -1, due t o the S - - N b o n d stretching v i b r a t i o n [12], is i n d e p e n d e n t from the s u b s t i t u e n t in the aniline, as f o u n d for t h e benzene derivatives [13]. I n particular, in N - m e t h y l - 2 - t h i o p h e n e s u l f o n a m i d e this b a n d is located at 835 em -1, as in N - m e t h y l - p - t o l u e n s u l f o n a m i d e [14]. Moreover in ~ a n d 7 pyridine derivatives t h e S - - N stretching v i b r a t i o n a l mode is p r o b a b l y a t 946-967 cm-~; its position could be different from t h a t f o u n d for the o t h e r 2-thiophenesulfonamides because of the imino s t r u c t u r e of the nitrogen atom. Acknowledgements.---The authors are grateful to the Consiglio Nazionale delle Ricerche (Rome)
for financial support. [8] L. S. FERGUSON, The modern Structural Theory of Organic Chemistry, p. 527. Prentice-Hall, Englewood Cliffs, New Jersey (1964). [9] L. J. BEI~AWIY, The Infrared Spectra of Complex Molecules, 2 ed, p. 357. Wiley, New York, (1958). [10] S. DETO~ and D. H.'~DzI,Spectrochim. Acta 9, 601 (1957); E. A. ROBINSON, Can. J. Chem. 39, 247 (1961); A. E. LUTSKI and I. K. Is~rcRENXO, Zh. Obshch. Khim. 38, 1618 (1968); Chem. Abstr. 69, 95730 (1968). [11] T. UNo, K. MACmDA and K. H~-~AI, Spe~troehim. Acta 24~k, 1705 (1968); N. S. HAM, A. lV[. H_~)~BLYand R. H. L~BY, Aust. J. Chem. 13, 443 (1960). [12] A. R. KATRrrz~Y and R. A. JONES, J. Chem. Soc. 4497 (1960); G. V ~ s ~ v ~ , Vibrational Spectra of Benzene Derivatives, p. 391. Academic Press, New York (1969). [13] V. L. LEVAS~OVAand N. P. Lus~rI~A, Zh. Prikl. Spe]ctrosb. 10, 502 (1969); Chem. Abstr. 70, 119753 (1969). [14] D. H~I)Zi, J. Chem. Soc. 847 (1957).