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Infra-red absorptions of sulphones
Spectrochimica Acta. 1960. YoJ. 16. pp . 1312 to 1317. P ergamon Press Ltd . Printed in Nort hern Ir eland
Infra-red absorptions of sulphones P. M. G. BAVIN, G. W . GRAY and A. STEPHENSON Che mist ry D ep art m ent , The U niversity, H ull (Received 14 J uly 1960 )
st rong absorption within t he lim its 1318-1 333 cm- I appears t o be characteri stic of t he > 8 0 2group in sulphones dissolve d in ca rbon tetrach loride. Th is absorption is acc ompanie d by one or often two weaker absorptions a t 1311 ± 5 crrr? and 1294 ± 8 cm" , unless t h e su lph ur atom is part of a fused five -membered ring. T he > 80 2 gro up is further characterized by at leas t one strong abso rption at 1165 ± 18 em-I. Th ese result s were obtained usin g solutions of twenty-three sulphones. Four ot her sulphones which were insoluble in carbon t etrachloride were examined as Nuj ol mulls, an d , allowing for shifts to lower frequencies, the spe ctra suppor t the suggest ion that a triple absorption in the region 1287-1 333 cm- I is frequently characteristic of a sulphone . The triple absorption wa s found for nineteen of t he twent y -seven sulp hones . Abstract~A
Introduction THE infra-red absorptions of sulp hones were first studied by SCHREIBER [1] who exa mined t welve comp ounds of t he t y pe R S0 2 .R ' containing gro ups R and R ' such as alkyl, alkenyl, aryl and substituted aryl. Solutions of t he compounds in carbon t etrachloride, chloro for m or acetonitrile were used. E ach sulphone absorbed strongly within t he limi t s 1128-1 H>5 cm- I and 1313-1345 em r -, and t he two maxima , which were absent fr om t he spectra of t he sulphides , were clearly distingui sh ed fr om neigh bouring absorptions whic h were weaker, except in t he case of di benzyl sulphone which absorbed more st rongly at 1120 cm ? t han at 1155 em- I. Fo ur other compounds-- p'-(pheny lsu lp honyl)ethylacetate and three containing more than one > S0 2 gro up in the molecule-were also stud ied , and t he overall resul t s showed that eac h of t he sixteen compounds absorbed strongly in t he region s 1128-11 59 cm- I and 1313-1 352 cm <, believe d t o be characteristic of t he > S0 2 group . BARNARD et al. [2] then showed that four sulp hone s, in carbon t etrachloride solution, gave two strong absorpt ions, one at 1130-1164 cm r ! and one at 1:U 2-1326 em- I, agreeing well with SCHREIBER'S data. The corresponding sulphoxides did not absorb within these limits. More recentl y , AMSTUTZ et al. [3] quoted an absorpt ion at 1130-11 54 cm" as char a ct eristi c of six sulpho nes (examined as solutions or m ulls) but did not me ntion t he other absorption at a higher frequency. WAIGHT [4] has reported one strong absorption in eac h of t he limit s 1134-11 67 cm - I and 1305-1 341 em"! for carbon tetrachloride solutions of six sulp hones, FIELD [5] has found t hat a Nujol mull of fJ-phenylethylsulphone abso rbs strong ly at 1139 [11 l2 ] l31 [41 [5 ]
K. C. S CHREIDER, A nal. Chern : 21, 1168 (1949). D . BARNARD, J . xr . FABIAN and H . P . KO CH, J. Chem , Soc. 2442 ( 1949 ). Eo D . AlIIST UTZ , I. xr. H U N SB EJ WER and J . J . C H ESBICK . J . A m . Ohem . Soc . 73, 1220 (1951). Eo S. l,V A I GH T . J . Chem . Soc. 2-140 (1952). L. FJELD, J. Am. Cheni, S oc. 74, 39 19 (1952).
131 2
I nfra -red absorptions of sulphones
and 1305 em:", and PRICE and GILLIS [6J and l >RICE and MORITA [7] have examined oil films of methylpropylsulphone, allylm eth ylsulphone, methylvinylsulphone , ,B-chloroet hy lpheny lsulphone and phenylvinylsulphone. In t hese cases, the st rongest ab sorp ti ons were t hose char act eristi c of the > S0 2 group, and lay , respectively, at 1124 and 1299-1316 cm: ", 1136 and 1299 em:", 1136 and 1316 em-I, 1155 and 1328 em:", and 1153 and 1324 crrr-' . Th e corresponding sulphides and sulphoxides were also st udied, and these absor pt ions were found to be absent or very much weaker t han for the sulphone . Making no allowance for t he different st ates in which sulphones have been examined in the abo ve work, it seems clear that the > S0 2 group in sulphones gives rise to st rong absorpt ions at II 24-1164 cm ? and 1299-1353 cm- ' .
Experimental During routine work, the infra-red spectra of carbon tetrachloride solutions of two sulphones derived from fluorene and repre sent ed by (I), where R = p-tolyl, and R' = methyl and isopropyl, were recorded using a Unicam S.P. 100 doublebeam infra-red spectrophotometer equipped with rock salt optics.
I I ·": Q;:&J .&
~
R'
SOzR
I
The regions 1280-1470 cm- and 1l00-1 200 em"! are free from any st rong absorpt ions from carbon t etrachloride, and compensat ed liquid cells were not required to det ect t he cha rac te rist ic > S0 2 bands . A cell of thickness of 0'5 mm was used , and contain ed an approximately I % solution of the sulphone . The absorptions for t he tw o sulphones are given in Tabl e 1. I
T a bl e I It (1) (1)
I
It '
p- to lyl
melhyl
1 100(w)
11 54( \'8)
11 70(v w)
1I S8(vw)
12%(111)
1 307(m )
1320 (8)
p-to}yl
isopro p yl
l11O( w)
11 54(\' 8)
11 75(\'11")
1187(w)
1288(m )
1306(m)
1320(8)
The single, symmetrical , and very strong ab sorption at 1154 cm:' and the stro ng absorpt ion at 1320 em:" given by both compounds agree well with the expec te d absorpt ion for the > S02 group. However, the occur rence of three absor ption maxima in the region from abo ut l ::WO t o 1320 cm- 1 appeared t o be a new feature, not evident from t he spectroscopic data published by earlier workers. T he a bsorpt ion bands obtained by SC HRE IB E R [I] at t hese frequencies were, however , very br oad , and it seemed possible t hat, under higher resoluti on , a triple ab sorption was being detect ed. Certainly, the corr esponden ce between t he fr equ encies of t he t hree ab sorp ti ons for t he two compounds was excellent, and, as the spectr um for 9-(9-isopropylfluorenyl-p- t olylsulphone illustrat es, t he t hree absorp ti ons, t he [6] C. C. [7] C. C.
PRICE PmCE
an d R. and H .
G. G ILLI S, J. Am . Chem , So c. 75, 47riO ( 1953). l\l OlUT A, J . Am. Chem , So c. 75, 4747 (J!J53 ).
1313
p, M,
G, BAVIN, G,
W,
and A.
GRAY
STEPHENSON
o
~ c
.Q
::l 'E
5
50
~
M
E
V
100
vJ
1400
1300
1200
1100
Fig. 1. Infra-red spectrum of 9-(9-isopropylfluorenyl)-p-tolylsulphone from 1100 -1400 em-I. S = solvent (carbon tetrachloride),
Table 2 Frequency
Compound It R R It R It R It It R It It R R It
methyl; R' ~ hydrogen ~ methyl; It' = methyl ~ methyl; It' = isopropyl = methyl; R' ~ allyl = methyl; R' ~ benzyl It' ~ hydrogen = allyl; = benzyl; R' ~ hydrogen ~ benzyl; R' = methyl = phenyl; R' = hydrogen = phenyl; R' ~ methyl ~ p-tolyl; It' = hydrogen? = p-tolyl; R' = methyl ~ p-tolyl; It' = ethyl (I) (1) ~ p-tolyl; It' = isopropyl (J) = p-tolyl; R' = allyl (1) It ~ p-tolyl; R' = benzyl (I) R = p-tolyl; R' oc phenyl Diphenylsulphone Dibenzylsulphone Jlenzyl-p-tolylsulphone p-Tolylsulphonylpiperidide Thionaphthene dioxide Dibenzothionaphthene dioxtdev (1) II) (I) (I) (1) (I) (I) (1) (I) (1) (1) (1)
=
(cirr')
1123(vs) 1121(s) 1128t(m)
1151(vs) 1152(vs) 1152(vs) 1147(vs)
1124(vs) I117(vs) 1130(s)
1162(w) 1150(vs) 1160(s)
1112(vs) 1125(vs) 1100(vs)
1314(s) 1298(m) 1296(s) 1808t(s) 1287(s) 1814t(vs) 1800t(m) 1298(w) 1302(m) 1229(m) 1296(s) 1800(w) 1315(w) 1816(m) 1299(w)
1183(s)
1154(vs) 1152(vs) 1154(vs) 11f,3(vs) 1152(vs) 1150(vs) 1166(vs) 1155 t(m) 1160(vs) 1160(vs) 1164(vs)
1180(m) 1178(s) 1188(s) 1183(s) 1180(m)
1296(m) 1295(w) 1288(m) 1297(w) l293(w) 1290(m) 1300(m) 1175(vs) 1177(m)
• Low solubility in carbon tetrachloride. t Shoulder on the side of a neighbouring strong absorption maximum.
1314
1282(s) 1200(s)
1297(w) 1290(w)
1807(m) 1306(m) 1306(m) 1308(w) 1306(m) l307(m) 18l2(s) 1308(m) 1308(w) r:108(8)
1325(vs) 1818(vs) 1820(vs) 1322(vs) 1318(s) 1880(vs) 1828(vs) 1320(vs) 1328(s) 1828(s) 1828(w) 1820(s) 1319(s) 1320(s) 1820(s) 1820(m) 1321(s) 1880(vs) 1388(vs) 1333(s) 1320(8) 1822(v8) 1828(w)
Infra-red absorptions of sulphones
strongest at 1320 em:", a moderately strong absorption at 1306 cm", and a stronger absorption at 1288 cm :", were well defined. A range of sulphones was therefore examined to establish whether this triple absorption is characteristic of the >S02 grouping. The spectra of the compounds listed in Table 2 were obtained from carbon tetrachloride solutions, though, in some cases, the solubilities of the sulphones in this solvent were quite low, and solutions of < 1 per cent concentration had to be employed. The compounds in the first part of Table 2 are derived from fluorene, and are distinguished by reference to structure (I) and the appropriate groups Rand R'. To simplify the data, only those absorptions which could be classed as strong or very strong are recorded in the range 1100-1200 crn:", except in cases in which the solubility ofthe compound was very low. All absorptions in the range 1283-1333 cm ? are recorded in an attempt to assess the significance of the triple absorption in this frequency range.
Discussion From Table 2, it is seen that eighteen of the twenty-three compounds give a single absorption, usually very strong, in the region 1147-1166 em-I. The five sulphones which do not absorb here do, however, absorb at about 1180 em-I. Considering the range 1147-1183 crrr", each of the compounds in Table 2 gives an absorption which may range from moderate to very strong, and three of the sulphones, p-tolylsulphonylpiperidide, (I), R = phenyl, R' = methyl, and (I), R = benzyl, R' = hydrogen, give two absorptions at 1160 and 1175 em:", 1160 and 1183 ern:", and 1162 and 1178 cm :", respectively. Nine of the sulphones give an additional strong or very strong absorption in the range 1100-1130 crrr". In one case, dibenzylsulphone, this absorption at 1125 crn ' ! is considerably more intense than the one at 1155 cmr". and this point was also noted by SCHREIBER [1]. It would appear that one and possibly two absorptions at 1147-1183 ern"! are characteristic of the >S02 group. If the absorption in the region 1112-1130 cm- I is also associated with this group, then thirteen of the sulphones give a single absorption, eight give two absorptions, and two give three absorptions in the overall range 1112-1183 em-I. These frequency limits are broader than any previously quoted, e.g. 1124-1164 cm ", but a rather wider range of compounds has now been studied. Fourteen of the twenty-three sulphones give three absorptions in the region 1287-1333 om:", and the frequency limits for each may be given as 1287-1302 em-I, 1306-1316 cm ? and 1318-1333 em-I. These limits correspond to the overall range of 1299-1345 cm-I quoted by previous workers for the >S02 group. The absorption of highest frequency is invariably the most intense, and the other two range from weak to very strong, the absorption at 1306-1316 em " being sometimes weaker and sometimes stronger than that at 1287-1302 cm". However, it would appear that this triple absorption is a reasonably characteristic feature of the infra-red spectra of sulphones, particularly as the frequencies of the three maxima fall within such narrow limits. Of the nine sulphones which did not give this triple absorption, one was the compound (I), R = p-tolyl, R' = hydrogen, which was rather insoluble in carbon tetrachloride. Using a Nujol mull of this compound, absorptions at 1295, 1307 1315
P . M.
G. B AVI N , G .
W.
GRAY
and A.
S TEP HENS ON
and 1313 cm-l were obtained , and the behaviour of the compound now confor ms to the gener al pattern, alt houg h the frequen cies of the absorp t ions ob tained fr om t he mull will be lower t han would have been obtained had a sufficiently strong solution been available. By examining a number of sulphones as solut ions and as mulls, it has been found t hat the decrease s in the fr equencies of the three ab sor pti on s on passing from a solut ion in carbon tetrachloride t o a mull are very varia ble, 2-25 em:", 3-1 5 em >' and 8- 19 ern"! for the t hree absorptions in ord er of inc reasin g fr equency. With six of the suiphones, t he middle a bsorption of t he triplet ap peared to be ab sent, and, with dibenzyl sulphone, a bsorpt ions wer e shown at 1308 and 1333 cm'<, but none in the range 1287-1302 ern>'. The occurre nce of a double rather t han a triple absorption cannot be attributed to a low solu bility of these compounds in car bon tetrachloride. The two sulphones, t hionaphthene dioxide and dibenzothionaphthene dioxide, which gave only one a bsorpt ion in the range 1287-1 333 cm :", were also examined as Nujol mulls, although the first of these compounds was quite soluble in carbon tetrachloride. In neither case was a triple ab sorption found in the spectrum of the mull, but it is interesting t o note that the sing le absorpt ion given by a solution of t hionaphthe ne di oxide at 1322 cm- l was replaced by two absorpt ions at 1275 and 1288 cm - l in the mull, a nd t he sing le absorption of dibenzothionaphthen e dioxide at 1323 cm- l likewise by t wo a bsorptions at 1275 and 1293 cm ? in t he m ull. Whatever t he ex pla nation of t his, it is not ewor thy that these t wo compounds, in which the sulph ur is part of a fu sed five-membered ring, const itute t he exce ption to the propo sal t hat a double or, more generally, a t riple a bsorption in the range 1287-1333 cm - l is characterist ic of a sulp hone . Finally it is not ed that all twenty-t hree compounds give an ab sorption at 1318-1333 cm:", and it appears t hat this absorp t ion is of great er di agn ostic value than the more variable absorption at ab ou t 1160 em-I. A st r ong absorpt ion at 1326 ± 8 em:" accompani ed by one or, more usu ally, two weaker a bsorptions at 1311 ± 5 cm-1 and 1294 ± 7 em- I- unless t he suphur ato m is p art of a fu sed five-membered ring-is char acterist ic of t he presence of the > 80 2 group which can be confirmed by the occurrence of at lea st one strong a bsorpt ion at 1165 ± 18 em-I. Four sulphones whi ch were too insoluble in carbon t etrachloride wer e exa mined as Nujol mulls. The main absorptions are given in T able 3, where the two hi ghest frequencies are associated with the C-N0 2 gro up . The strong ab sorption at about 1150 cm-l is ag ain observed, although the fr equency may be up t o 7 em>' lower than for the solut ion state . Each of t he compounds absorbs within the limits 1295 ± 5 cm" , 1304 ± 2 cm " ! and 1314 ± 4 em :", corr esp onding well with the limits qu ot ed earlier for t he fourteen compo unds in Tabl e 2, when allowan ce is made for the kn own freque ncy shift s whi ch accompany a change of st ate fr om solution t o mull. Neither I % carbon tet rachloride solutions nor mulls of t he following sulphidesbenzyl-9-fluorenylsulphide, dibenzylsulphide, 9-(9-methylfluorenyl)phenylsulphide, 9-fluoren yl-p -toly lsulp hide and 9-fluorenylphenylsulphide-absorb in t he r an ges 1100-1183 cm" and 1287-1333 cm- l characterist ic of the > 80 2 gro up . This is also true for benzyl-9-f1uoren ylsulphoxide whi ch ab sorbs st r ongly, as a KBr di sk , 1316
Infra-red absorptions of sulphones
Table 3 Frequency (em-i)
Compound
1150(s)
Me-o--S02.CH2-Q-N02 ..-Q-SO'CH'Yo, N0
1174(m)
1295(m)
1302(m)
1317(s)
1344
1525
1152(s)
1300(s)
1302(s)
1317(s)
1345
1521
1152(s)
1292(8)
1303(s)
1312(s)
1343
1512
1152(s)
1290(s)
~305(.3)
1310(s)
1354
1533
2
at 1040 em>'. A weaker absorption at 1070 cm-1 is also given, comparing with one at 1077 cm- 1 for a solution of the corresponding sulphide. Finally, we can compare the frequencies of the strongest absorptions for diphenyl and dibenzyl suIphones obtained in this work with those reported by other workers. Table 4 Ref. no. Diphenylsulphone Dibenzylsulphone
[1]
1155; 1325 cm~lo 1120; 1155; 1325 em-it
[2] 1164; 1336 em-I:::
[4] 1160; 1329 em-I:::
Present study 1166- 1330 em-1+ 1125; 1155; 1333 em-I:::
* Solution in carbon tetrachloride aud aeetonitr.ile.
t Solution in acetonitrile. t Solution in carbon tetrachloride.
Materials The fluorene sulphones have already been described [8, 9], and the following sulphones were prepared by oxidizing the pure monosulphides with 5% hydrogen peroxide in acetic acid [10]: diphenylsulphone, dibenzylsulphone, thionaphthene dioxide, dibenzothionaphthene dioxide. Benzyl p-tolylsulphone, p-nitrobenzyl-p-tolylsulphone and 2:4-dinitrobenzylp-tolylsulphone were prepared by reacting sodium p-toluenesulphinate with the appropriate halide [11]. p-Tolylsulphonylpiperidide was prepared from p-toluenesulphonylchloride and piperidine. All compounds gave melting points which agreed with literature values [II, 12]. [8] [9] [10] [11] [12]
P. M. G. BAVIN, Can. J. Chem. 38, 917 (1960). P. M. G. BAVIN. In preparation. M. GAZDAR and S. SMILES, J. Ohem, Soc. 93, 1834 (1908). R. L. SHRINER and S. O. GREENLEE, J. Orq. Chem, 4, 242 (1939). Beilstein's Handbuch der Organischen Chemie, Springer, Berlin (1918-1960).
1317
Infra-red absorptions of sulphones P. M. G. BAVIN, G. W . GRAY and A. STEPHENSON Che mist ry D ep art m ent , The U niversity, H ull (Received 14 J uly 1960 )
st rong absorption within t he lim its 1318-1 333 cm- I appears t o be characteri stic of t he > 8 0 2group in sulphones dissolve d in ca rbon tetrach loride. Th is absorption is acc ompanie d by one or often two weaker absorptions a t 1311 ± 5 crrr? and 1294 ± 8 cm" , unless t h e su lph ur atom is part of a fused five -membered ring. T he > 80 2 gro up is further characterized by at leas t one strong abso rption at 1165 ± 18 em-I. Th ese result s were obtained usin g solutions of twenty-three sulphones. Four ot her sulphones which were insoluble in carbon t etrachloride were examined as Nuj ol mulls, an d , allowing for shifts to lower frequencies, the spe ctra suppor t the suggest ion that a triple absorption in the region 1287-1 333 cm- I is frequently characteristic of a sulphone . The triple absorption wa s found for nineteen of t he twent y -seven sulp hones . Abstract~A
Introduction THE infra-red absorptions of sulp hones were first studied by SCHREIBER [1] who exa mined t welve comp ounds of t he t y pe R S0 2 .R ' containing gro ups R and R ' such as alkyl, alkenyl, aryl and substituted aryl. Solutions of t he compounds in carbon t etrachloride, chloro for m or acetonitrile were used. E ach sulphone absorbed strongly within t he limi t s 1128-1 H>5 cm- I and 1313-1345 em r -, and t he two maxima , which were absent fr om t he spectra of t he sulphides , were clearly distingui sh ed fr om neigh bouring absorptions whic h were weaker, except in t he case of di benzyl sulphone which absorbed more st rongly at 1120 cm ? t han at 1155 em- I. Fo ur other compounds-- p'-(pheny lsu lp honyl)ethylacetate and three containing more than one > S0 2 gro up in the molecule-were also stud ied , and t he overall resul t s showed that eac h of t he sixteen compounds absorbed strongly in t he region s 1128-11 59 cm- I and 1313-1 352 cm <, believe d t o be characteristic of t he > S0 2 group . BARNARD et al. [2] then showed that four sulp hone s, in carbon t etrachloride solution, gave two strong absorpt ions, one at 1130-1164 cm r ! and one at 1:U 2-1326 em- I, agreeing well with SCHREIBER'S data. The corresponding sulphoxides did not absorb within these limits. More recentl y , AMSTUTZ et al. [3] quoted an absorpt ion at 1130-11 54 cm" as char a ct eristi c of six sulpho nes (examined as solutions or m ulls) but did not me ntion t he other absorption at a higher frequency. WAIGHT [4] has reported one strong absorption in eac h of t he limit s 1134-11 67 cm - I and 1305-1 341 em"! for carbon tetrachloride solutions of six sulp hones, FIELD [5] has found t hat a Nujol mull of fJ-phenylethylsulphone abso rbs strong ly at 1139 [11 l2 ] l31 [41 [5 ]
K. C. S CHREIDER, A nal. Chern : 21, 1168 (1949). D . BARNARD, J . xr . FABIAN and H . P . KO CH, J. Chem , Soc. 2442 ( 1949 ). Eo D . AlIIST UTZ , I. xr. H U N SB EJ WER and J . J . C H ESBICK . J . A m . Ohem . Soc . 73, 1220 (1951). Eo S. l,V A I GH T . J . Chem . Soc. 2-140 (1952). L. FJELD, J. Am. Cheni, S oc. 74, 39 19 (1952).
131 2
I nfra -red absorptions of sulphones
and 1305 em:", and PRICE and GILLIS [6J and l >RICE and MORITA [7] have examined oil films of methylpropylsulphone, allylm eth ylsulphone, methylvinylsulphone , ,B-chloroet hy lpheny lsulphone and phenylvinylsulphone. In t hese cases, the st rongest ab sorp ti ons were t hose char act eristi c of the > S0 2 group, and lay , respectively, at 1124 and 1299-1316 cm: ", 1136 and 1299 em:", 1136 and 1316 em-I, 1155 and 1328 em:", and 1153 and 1324 crrr-' . Th e corresponding sulphides and sulphoxides were also st udied, and these absor pt ions were found to be absent or very much weaker t han for the sulphone . Making no allowance for t he different st ates in which sulphones have been examined in the abo ve work, it seems clear that the > S0 2 group in sulphones gives rise to st rong absorpt ions at II 24-1164 cm ? and 1299-1353 cm- ' .
Experimental During routine work, the infra-red spectra of carbon tetrachloride solutions of two sulphones derived from fluorene and repre sent ed by (I), where R = p-tolyl, and R' = methyl and isopropyl, were recorded using a Unicam S.P. 100 doublebeam infra-red spectrophotometer equipped with rock salt optics.
I I ·": Q;:&J .&
~
R'
SOzR
I
The regions 1280-1470 cm- and 1l00-1 200 em"! are free from any st rong absorpt ions from carbon t etrachloride, and compensat ed liquid cells were not required to det ect t he cha rac te rist ic > S0 2 bands . A cell of thickness of 0'5 mm was used , and contain ed an approximately I % solution of the sulphone . The absorptions for t he tw o sulphones are given in Tabl e 1. I
T a bl e I It (1) (1)
I
It '
p- to lyl
melhyl
1 100(w)
11 54( \'8)
11 70(v w)
1I S8(vw)
12%(111)
1 307(m )
1320 (8)
p-to}yl
isopro p yl
l11O( w)
11 54(\' 8)
11 75(\'11")
1187(w)
1288(m )
1306(m)
1320(8)
The single, symmetrical , and very strong ab sorption at 1154 cm:' and the stro ng absorpt ion at 1320 em:" given by both compounds agree well with the expec te d absorpt ion for the > S02 group. However, the occur rence of three absor ption maxima in the region from abo ut l ::WO t o 1320 cm- 1 appeared t o be a new feature, not evident from t he spectroscopic data published by earlier workers. T he a bsorpt ion bands obtained by SC HRE IB E R [I] at t hese frequencies were, however , very br oad , and it seemed possible t hat, under higher resoluti on , a triple ab sorption was being detect ed. Certainly, the corr esponden ce between t he fr equ encies of t he t hree ab sorp ti ons for t he two compounds was excellent, and, as the spectr um for 9-(9-isopropylfluorenyl-p- t olylsulphone illustrat es, t he t hree absorp ti ons, t he [6] C. C. [7] C. C.
PRICE PmCE
an d R. and H .
G. G ILLI S, J. Am . Chem , So c. 75, 47riO ( 1953). l\l OlUT A, J . Am. Chem , So c. 75, 4747 (J!J53 ).
1313
p, M,
G, BAVIN, G,
W,
and A.
GRAY
STEPHENSON
o
~ c
.Q
::l 'E
5
50
~
M
E
V
100
vJ
1400
1300
1200
1100
Fig. 1. Infra-red spectrum of 9-(9-isopropylfluorenyl)-p-tolylsulphone from 1100 -1400 em-I. S = solvent (carbon tetrachloride),
Table 2 Frequency
Compound It R R It R It R It It R It It R R It
methyl; R' ~ hydrogen ~ methyl; It' = methyl ~ methyl; It' = isopropyl = methyl; R' ~ allyl = methyl; R' ~ benzyl It' ~ hydrogen = allyl; = benzyl; R' ~ hydrogen ~ benzyl; R' = methyl = phenyl; R' = hydrogen = phenyl; R' ~ methyl ~ p-tolyl; It' = hydrogen? = p-tolyl; R' = methyl ~ p-tolyl; It' = ethyl (I) (1) ~ p-tolyl; It' = isopropyl (J) = p-tolyl; R' = allyl (1) It ~ p-tolyl; R' = benzyl (I) R = p-tolyl; R' oc phenyl Diphenylsulphone Dibenzylsulphone Jlenzyl-p-tolylsulphone p-Tolylsulphonylpiperidide Thionaphthene dioxide Dibenzothionaphthene dioxtdev (1) II) (I) (I) (1) (I) (I) (1) (I) (1) (1) (1)
=
(cirr')
1123(vs) 1121(s) 1128t(m)
1151(vs) 1152(vs) 1152(vs) 1147(vs)
1124(vs) I117(vs) 1130(s)
1162(w) 1150(vs) 1160(s)
1112(vs) 1125(vs) 1100(vs)
1314(s) 1298(m) 1296(s) 1808t(s) 1287(s) 1814t(vs) 1800t(m) 1298(w) 1302(m) 1229(m) 1296(s) 1800(w) 1315(w) 1816(m) 1299(w)
1183(s)
1154(vs) 1152(vs) 1154(vs) 11f,3(vs) 1152(vs) 1150(vs) 1166(vs) 1155 t(m) 1160(vs) 1160(vs) 1164(vs)
1180(m) 1178(s) 1188(s) 1183(s) 1180(m)
1296(m) 1295(w) 1288(m) 1297(w) l293(w) 1290(m) 1300(m) 1175(vs) 1177(m)
• Low solubility in carbon tetrachloride. t Shoulder on the side of a neighbouring strong absorption maximum.
1314
1282(s) 1200(s)
1297(w) 1290(w)
1807(m) 1306(m) 1306(m) 1308(w) 1306(m) l307(m) 18l2(s) 1308(m) 1308(w) r:108(8)
1325(vs) 1818(vs) 1820(vs) 1322(vs) 1318(s) 1880(vs) 1828(vs) 1320(vs) 1328(s) 1828(s) 1828(w) 1820(s) 1319(s) 1320(s) 1820(s) 1820(m) 1321(s) 1880(vs) 1388(vs) 1333(s) 1320(8) 1822(v8) 1828(w)
Infra-red absorptions of sulphones
strongest at 1320 em:", a moderately strong absorption at 1306 cm", and a stronger absorption at 1288 cm :", were well defined. A range of sulphones was therefore examined to establish whether this triple absorption is characteristic of the >S02 grouping. The spectra of the compounds listed in Table 2 were obtained from carbon tetrachloride solutions, though, in some cases, the solubilities of the sulphones in this solvent were quite low, and solutions of < 1 per cent concentration had to be employed. The compounds in the first part of Table 2 are derived from fluorene, and are distinguished by reference to structure (I) and the appropriate groups Rand R'. To simplify the data, only those absorptions which could be classed as strong or very strong are recorded in the range 1100-1200 crn:", except in cases in which the solubility ofthe compound was very low. All absorptions in the range 1283-1333 cm ? are recorded in an attempt to assess the significance of the triple absorption in this frequency range.
Discussion From Table 2, it is seen that eighteen of the twenty-three compounds give a single absorption, usually very strong, in the region 1147-1166 em-I. The five sulphones which do not absorb here do, however, absorb at about 1180 em-I. Considering the range 1147-1183 crrr", each of the compounds in Table 2 gives an absorption which may range from moderate to very strong, and three of the sulphones, p-tolylsulphonylpiperidide, (I), R = phenyl, R' = methyl, and (I), R = benzyl, R' = hydrogen, give two absorptions at 1160 and 1175 em:", 1160 and 1183 ern:", and 1162 and 1178 cm :", respectively. Nine of the sulphones give an additional strong or very strong absorption in the range 1100-1130 crrr". In one case, dibenzylsulphone, this absorption at 1125 crn ' ! is considerably more intense than the one at 1155 cmr". and this point was also noted by SCHREIBER [1]. It would appear that one and possibly two absorptions at 1147-1183 ern"! are characteristic of the >S02 group. If the absorption in the region 1112-1130 cm- I is also associated with this group, then thirteen of the sulphones give a single absorption, eight give two absorptions, and two give three absorptions in the overall range 1112-1183 em-I. These frequency limits are broader than any previously quoted, e.g. 1124-1164 cm ", but a rather wider range of compounds has now been studied. Fourteen of the twenty-three sulphones give three absorptions in the region 1287-1333 om:", and the frequency limits for each may be given as 1287-1302 em-I, 1306-1316 cm ? and 1318-1333 em-I. These limits correspond to the overall range of 1299-1345 cm-I quoted by previous workers for the >S02 group. The absorption of highest frequency is invariably the most intense, and the other two range from weak to very strong, the absorption at 1306-1316 em " being sometimes weaker and sometimes stronger than that at 1287-1302 cm". However, it would appear that this triple absorption is a reasonably characteristic feature of the infra-red spectra of sulphones, particularly as the frequencies of the three maxima fall within such narrow limits. Of the nine sulphones which did not give this triple absorption, one was the compound (I), R = p-tolyl, R' = hydrogen, which was rather insoluble in carbon tetrachloride. Using a Nujol mull of this compound, absorptions at 1295, 1307 1315
P . M.
G. B AVI N , G .
W.
GRAY
and A.
S TEP HENS ON
and 1313 cm-l were obtained , and the behaviour of the compound now confor ms to the gener al pattern, alt houg h the frequen cies of the absorp t ions ob tained fr om t he mull will be lower t han would have been obtained had a sufficiently strong solution been available. By examining a number of sulphones as solut ions and as mulls, it has been found t hat the decrease s in the fr equencies of the three ab sor pti on s on passing from a solut ion in carbon tetrachloride t o a mull are very varia ble, 2-25 em:", 3-1 5 em >' and 8- 19 ern"! for the t hree absorptions in ord er of inc reasin g fr equency. With six of the suiphones, t he middle a bsorption of t he triplet ap peared to be ab sent, and, with dibenzyl sulphone, a bsorpt ions wer e shown at 1308 and 1333 cm'<, but none in the range 1287-1302 ern>'. The occurre nce of a double rather t han a triple absorption cannot be attributed to a low solu bility of these compounds in car bon tetrachloride. The two sulphones, t hionaphthene dioxide and dibenzothionaphthene dioxide, which gave only one a bsorpt ion in the range 1287-1 333 cm :", were also examined as Nujol mulls, although the first of these compounds was quite soluble in carbon tetrachloride. In neither case was a triple ab sorption found in the spectrum of the mull, but it is interesting t o note that the sing le absorpt ion given by a solution of t hionaphthe ne di oxide at 1322 cm- l was replaced by two absorpt ions at 1275 and 1288 cm - l in the mull, a nd t he sing le absorption of dibenzothionaphthen e dioxide at 1323 cm- l likewise by t wo a bsorptions at 1275 and 1293 cm ? in t he m ull. Whatever t he ex pla nation of t his, it is not ewor thy that these t wo compounds, in which the sulph ur is part of a fu sed five-membered ring, const itute t he exce ption to the propo sal t hat a double or, more generally, a t riple a bsorption in the range 1287-1333 cm - l is characterist ic of a sulp hone . Finally it is not ed that all twenty-t hree compounds give an ab sorption at 1318-1333 cm:", and it appears t hat this absorp t ion is of great er di agn ostic value than the more variable absorption at ab ou t 1160 em-I. A st r ong absorpt ion at 1326 ± 8 em:" accompani ed by one or, more usu ally, two weaker a bsorptions at 1311 ± 5 cm-1 and 1294 ± 7 em- I- unless t he suphur ato m is p art of a fu sed five-membered ring-is char acterist ic of t he presence of the > 80 2 group which can be confirmed by the occurrence of at lea st one strong a bsorpt ion at 1165 ± 18 em-I. Four sulphones whi ch were too insoluble in carbon t etrachloride wer e exa mined as Nujol mulls. The main absorptions are given in T able 3, where the two hi ghest frequencies are associated with the C-N0 2 gro up . The strong ab sorption at about 1150 cm-l is ag ain observed, although the fr equency may be up t o 7 em>' lower than for the solut ion state . Each of t he compounds absorbs within the limits 1295 ± 5 cm" , 1304 ± 2 cm " ! and 1314 ± 4 em :", corr esp onding well with the limits qu ot ed earlier for t he fourteen compo unds in Tabl e 2, when allowan ce is made for the kn own freque ncy shift s whi ch accompany a change of st ate fr om solution t o mull. Neither I % carbon tet rachloride solutions nor mulls of t he following sulphidesbenzyl-9-fluorenylsulphide, dibenzylsulphide, 9-(9-methylfluorenyl)phenylsulphide, 9-fluoren yl-p -toly lsulp hide and 9-fluorenylphenylsulphide-absorb in t he r an ges 1100-1183 cm" and 1287-1333 cm- l characterist ic of the > 80 2 gro up . This is also true for benzyl-9-f1uoren ylsulphoxide whi ch ab sorbs st r ongly, as a KBr di sk , 1316
Infra-red absorptions of sulphones
Table 3 Frequency (em-i)
Compound
1150(s)
Me-o--S02.CH2-Q-N02 ..-Q-SO'CH'Yo, N0
1174(m)
1295(m)
1302(m)
1317(s)
1344
1525
1152(s)
1300(s)
1302(s)
1317(s)
1345
1521
1152(s)
1292(8)
1303(s)
1312(s)
1343
1512
1152(s)
1290(s)
~305(.3)
1310(s)
1354
1533
2
at 1040 em>'. A weaker absorption at 1070 cm-1 is also given, comparing with one at 1077 cm- 1 for a solution of the corresponding sulphide. Finally, we can compare the frequencies of the strongest absorptions for diphenyl and dibenzyl suIphones obtained in this work with those reported by other workers. Table 4 Ref. no. Diphenylsulphone Dibenzylsulphone
[1]
1155; 1325 cm~lo 1120; 1155; 1325 em-it
[2] 1164; 1336 em-I:::
[4] 1160; 1329 em-I:::
Present study 1166- 1330 em-1+ 1125; 1155; 1333 em-I:::
* Solution in carbon tetrachloride aud aeetonitr.ile.
t Solution in acetonitrile. t Solution in carbon tetrachloride.
Materials The fluorene sulphones have already been described [8, 9], and the following sulphones were prepared by oxidizing the pure monosulphides with 5% hydrogen peroxide in acetic acid [10]: diphenylsulphone, dibenzylsulphone, thionaphthene dioxide, dibenzothionaphthene dioxide. Benzyl p-tolylsulphone, p-nitrobenzyl-p-tolylsulphone and 2:4-dinitrobenzylp-tolylsulphone were prepared by reacting sodium p-toluenesulphinate with the appropriate halide [11]. p-Tolylsulphonylpiperidide was prepared from p-toluenesulphonylchloride and piperidine. All compounds gave melting points which agreed with literature values [II, 12]. [8] [9] [10] [11] [12]
P. M. G. BAVIN, Can. J. Chem. 38, 917 (1960). P. M. G. BAVIN. In preparation. M. GAZDAR and S. SMILES, J. Ohem, Soc. 93, 1834 (1908). R. L. SHRINER and S. O. GREENLEE, J. Orq. Chem, 4, 242 (1939). Beilstein's Handbuch der Organischen Chemie, Springer, Berlin (1918-1960).
1317