Gas—liquid chromatographic analyses

Journal of Chromatography, 321 (1985) lls125 Elsevier Science htblishers B.V., Amsterdam -

Printed in The Netherlands

CHROM. 17,388

GAS-LIQUID

CHROMATOGRAPHIC

ANALYSES

XXXII*. INCREMENTAL EFFECTS OF HYDROXY, METHOXY AND ACETOXY GROUPS INTRODUCED INTO ISOMERIC CHLOROBENZENES

ILPO 0.0.

KORHONEN

Department of Chemistry, University of Jyv&ky& Kyllikinkatu 1-3, SF-40100 Jyvtikylc? 10 (Finlund) (Received October 13th, 1984)

SUMMARY

Incremental effects of the additional hydroxy, methoxy and acetoxy groups introduced into various non-chlorinated and chlorinated positions of isomeric chlorobenzenes have been investigated on low-polarity and polar capillary columns isothermally at 160°C. On low-polarity columns the retention increments for chlorophenols varied from - 59 to 359 index units (i.u.), being in the ranges -30-260 i.u. with chloroanisoles and 68-363 iu. with chlorophenyl acetates. On polar columns the retentions were markedly enhanced, viz., up to 352-1293 i.u. for phenols, -3471 i.u. for anisoles and 223-600 iu. for phenyl acetates. The m- and p-hydroxy substitutions maximized the retention enhancements, which were markedly reduced with the o-hydroxy substitution. The effects of the other substituents are not so significant.

INTRODUCTION

Recently, a series of gas chromatographic (GC) studies aimed a maximizing the separation of complex mixtures of various chlorinated aromatics have been carried out, using temperature programming and low-polarity and polar capillary columnsl. The retention indices and the retention index increments for each position of substitution, together with the effect of increasing temperature on the values, have been discussed for seven groups of chlorinated aromatics, viz., benzenes2, phenols3, anisoles4, phenyl acetate$, veratrole@, 2-hydroxybenzaldehydes’ and 4-hydroxybenzaldehydes’ . This paper extends the earlier studies2+ by showing the retention increments of the OH, CH30 and CHJCOO groups introduced into various non-chlorinated and chlorinated positions of isomeric chlorobenzenes. The effects of each of the three substituents on both low-polarity and polar capillary columns based on the retention index data reported previously2-s are discussed. l

For Part XXXI, see ref. 3.

0021-9673/85/$03.30

0

1985 Eisevier Science Publishers B.V.

116

I. 0.0.

KORHONEN

EXPERIMENTAL

Materials Chlorobenzenes and chlorophenols were commercial products (Fluka, Buchs, Switzerland). Chlorophenols were converted into chloroanisoles4 and chlorophenyl acetates5 by using the known methylation and acetylation methods. Commercial mixtures of n-alkanes were obtained from different sources. Method GC analyses were carried out on a Varian Model 2400 gas chromatograph or on a Perkin-Elmer Sigma 3 instrument under the operating conditions reported earlier2+. Different glass or quartz capillary columns with low-polarity (SE-30) and polar (Carbowax 20M, OV-351 or FFAP) stationary phases were used. All data presented were recorded isothermally at 160°C and the retention indices were determined as described previously2+. RESULTS AND DISCUSSION

Additional group introduced into non-chlorinated positions of tiomeric chlorobenzenes Incremental effects due to an additional hydroxy, methoxy and acetoxy group introduced into different non-chlorinated positions of isomeric chlorobenzenes, i.e., AI = I,,cl (isomer formed) - I,ci (benzene), obtained on low-polarity and polar capillary columns are presented in Table I and Figs. 1 and 2. A summary of the increments is shown in Table II and the differences in the values between the three groups are given in Table III. With the monochloro isomers the greatest retention enhancements are shown by most bulky phenyl acetates, those of the 3- and Cchloro isomers being about 360 retention index units (i.u.), reducing to ca. 330 i.u. with the 2-chloro isomer. Owing to the smaller size of the methoxy substituent, the increments with chloroanisoles fall from 74 to 113 i.u., the 2-chloro isomer showing the highest increase4. The differences between the increments for isomeric monochlorinated phenyl acetates and anisoles are small, in contrast to those of chlorophenols. Owing to the artho-effect, only an enhancement of 151 i.u. for 2chlorophenol is observed, the retention increasing up to 3 17 i.u. with the 3-(m-) and C@-)chlorophenols. The values of the latter are 72 and 63 i.u. higher, respectively, than those of the corresponding more bulky anisoles, owing to the increased polarity of phenols, giving rise to enhanced retention also on the low-polarity columns. With higher chlorinated isomers the increments generally fall, the trends being almost the same as with the monochloro isomers. The hydroxy and acetoxy groups introduced into isolated positions, i.e., positions without adjecent chlorine atoms of the 1,2- and 1,3-d& and 1,2,3-trichlorobenzenes, show the highest increments, the values for the 3,4- and 3,5-d& and 3,4,5trichlorophenols being higher than those of the corresponding phenyl acetates and even higher than those for 3- and Ldchlorophenols (Table I, Fig. 1). With chlorinated anisoles, however, the greatest enhancements are shown by the vicinally substituted 2,3-di-, 2,3,4-n% and 2,3,4,%tetrachloro isomers owing to the steric effect reported earlier+. Anisoles and phenyl acetates with two adjacent chlorine atoms, i.e., the 2,6-d&, 2,3,6- and 2,4,6-t&, 2,3,4,6- and

117

GLC ANALYSES. XxX11. LOW -POLAR

COLUHYS

4

T

i

I

i

:

I

I

’

1

i

: 2

I

2:

26

4

Fig. 1. Incremental effects due to additional hydroxy, methoxy and acetoxy groups introduced into various non-chlorinated positions of isomeric chlorobenzenes, obtained on low-polarity capillary columns at MOT (Table I). (A) Phenol; (0) anisole; (0) phenyl acetate. The numbers indicate the positions of chlorination.

POLAR

COtUMNS

,

L-

i 23

I

25

26

ISOMER

Fig. 2. Effects as in Fig. 1, obtained on polar capillary cohmm~ at 160°C (Table I).

(496) (6) (3) (5) (2,4,6) (5)

(596) (496) (396)

1,2,31,2,41,2,4-

1,2,3,41,2,3,51,2,4,5-

184 328 359

2,6-

2,3,4,5,6-

2,3,4,62,3,5,6-

2,3,4,5-

2,3,42,3,52,3,62,4,52,4,63,4,5-

195

148 194 186

135 134 161 163 196 359

130 154 154

2,32,4-2.5-

3,43.5-

151 317 317

Phenol*: AIoii@

174

245 176 174

260 244 178 240 183 226

182 235 227

259 256 248

259 245 254

283

291 273 268

297 283 270 288 270 315

280 327 318

300 301 301

333 358 363

822

822 768 760

718 750 715 800 756 1293

663 1217 1241

646 717 689

1101 1101

596

Phenol:

AIons”

Phenyl acetate6:

AIowcns I

A&?

Polar

Anisole*:

Low-polarity

COhlt?Ul

234-

Chloro isomer foFmed

* For the retention indices of chlorobenzenes, see ref. 2. ** For the retention indices of chlorophenols, see ref. 3. For the retention indices of chloroanisoles, see ref. 4. 0 For the retention indices of chlorophenyl acetates, see ref. 5. R AI = I~n-ijC1 (isomer formed) - I.c, (benzene).

1,2,3,4,5-

(6)

(2) (495) (5)

1,31,21,3-

1,2,41,3,51,2,3-

(3,6) (496) (2,3,5,6)

1,21,31,4-

(U)

(395) (4)

I-

lI-

ChIorobenzene isomer* with (in parentheses) positions of additiona gFOUpS

A&ok*:

Phenyl acetatd:

280

432 285 278

402

425 450 432

498

464 486 480 490 480 432 290 427 292 345

537 558 530

538 552 515

559 578 600

AIci~oca~@

469

298 385 366

463 471 421

420 358 386

AIoca,@

INTO ISOMERIC

627

674 574 574

583 616 554 637 560 934

882

889

479

516 563 535

445 784 784

AIoa@

106

187 109 104

209 188 112 187 109 119

116 150 139

204 215 173

161 113 132

&~a,~

201 181 216 192 220 165

257 231 212

238 251 214

226 220 237

AIocwas@

DireFence: polar - low-polarity

INCREMENTAL EFFECTS DUE TO THE ADDITIONAL HYDROXY, METHOXY AND ACETOXY GROUPS INTRODUCED CHLOROBENZENES, OBTAINED ON LOW-POLARITY AND POLAR CAPILLARY COLUMNS AT 16o’C

TABLE I z 00

GLC ANALYSES. XXXII.

I19

l

23456I , I I

2,3,4,52,3,4,62,3,5,6-

19

-

88

- 143 - 79 - 82

-162 - 149 -109 - 125 - 14 44

-170 - 147 - 147 - 96 1 41

- 182 - 41 -46

-

AIosr - &coc,*

109

97 94

46

31 39 92 48 87 89

41 45 53 98 92 91

74 113 109

128

&cocn~

-

&cs*

For the retention increments of the components, see Tables I and IV.

21

91 18 12

- 125 -110 - 17 - 77 13 133

2,3,42,3,52,3,62,4,5-

-

-129 - 102 - 94 2 93 132

2,32,42,52,63,43,5-

2,4,6 3,4,5-

-108 72 63

49

Alon - &cH~*

Low-polarity

Column

234-

Parent-

Isomer

DIFFERENCES IN THE RETENTION INCREMENTS BETWEEN CHLORINATED ON LOW-POLARITY AND POLAR CAPILLARY COLUMNS AT 160°C

TABLE III

542

390 483 482

249 318 425 373 464 948

183 246 268 365 832 875

176 743 715

627

Afo,

Polar -

l

LJ&cH~

420

397 318 328

220 286 229 320 266 813

108 165 174 126 659 711

37 523 501

361

A~OII-

hcoc~~*

P

$! 8

154 122

kz

g

-1 165

P

?

A&rx+

135

-

32 1% 53 198

29

75 81 94 239 173 164

139 220 214

260

&coca

PHENOLS, ANISOLES AND PHENYL ACETATES, OBTAINED

E

121

GLC ANALYSES. XxX11.

2,3,5,6-tetra- and pentachloro isomers, show the smallest enhancements. Owing to the competing chlorine atoms, the steric effect in anisoles is prevented and the orfhoeffect in o,o’-chlorophenols is not as pronounced as with the o-isomers, the latter always giving smaller retention enhancements (Tables I and II). As a summary of the data presented in Table III, it can be seen that on lowpolarity columns the differences between the increments for phenols and anisoles varied from - 129 (2,3-isomer) to 133 i.u. (3,4,5-isomer) for phenols and phenyl acetates from - 182 (2-isomer) to 44 i.u. (3,4,5isomer) and for phenyl acetates and anisoles from 37 (2,3,4-isomer) to 113 i.u. (3-isomer). With the polar columns the retention increments are markedly increased, particularly in the case of chlorophenols (Tables I-III and Figs. 2 and 3). The effects indicated above are generally observed, the variation shown being more pronounced owing to the polar components on more polar stationary phases. Chlorophenols always show the highest increments, the differences between chlorophenyl acetates varying from 37 (Zisomer) up to 813 i.u. (3,4,Sisomer) (Table III). The differences between phenols and anisoles are from -7 to 239 i.u. higher, being in the range 176 (Zisomer) -948 i.u. (3,4,5Gsomer). In contrast to the lowpolarity columns, 2,3,4,5-tetrachloroanisole shows a 7 i.u. higher enhancement than the corresponding phenyl acetate. This phenomenon supports the assumption of a steric effect in a-chloroanisoles4, this effect not occurring or having a negligible influence in o,o’-chloroanisoles and o- and o,o’-chlorophenyl acetates. This can also be seen from the relatively smaller differences between the increments for the 2,3-, 2,4and 2,5-d& and 2,3,4-, 2,3,5- and 2,4,5_trichloro isomers in these two series, compared with the other isomers, the differences being much more pronounced on the polar columns4, as expected (Table III and Fig. 3). The enhanced retention increments of the various isomers are shown in Table I and Fig. 3, falling into two general groups with chlorophenols (o-isomers and mand p-isomers) and chloroanisoles (o-isomers and the other isomers) (Table II). Chlorophenyl acetates, however, show variable values. 4

POLAR

-

LOW- POLAR

Fig. 3. Subtractions of the retention increments, i.e., dlplpr EDIU,,,..- dI,lm-polunycolulaas, of three groups of chlorinated aromatics (Table I). (A) Phenol; (a) anisole; (0) phenyl acetate. The numbers indicate the positions of chlorination.

113

154 92 87

137 132 75 137 76 199

122 124 124 68 184 184

123 182 187

168

* For the retention indices of chlorobenzenes, see ref. 2. ** For the retention indices of chlorophenols, see ref. 3. ** For the retention indices of chloroanisoles, see ref. 4. 5 For the retention indices of chlorophenyl acetates, see ref. 5. @ AI = I,-,,, (isomer formed) - I,, (benzene).

4

25

23456, , , ,

(all)

“;z

108 -5 -7

11 13 5

2,3,4,52,3,4,62,3,5,6-

(l-5)

1,2,3,4,51,2,3,4,51,2,3,4,5-

loo 93 -17 89 -11 110

-25 -17 -34 12 2 243

2,3,42,3,52,3,62,4,52,4,63,4,5-

(194) (1,3) (2,3) (all) (2) (5)

1,2,3,41,2,3,51,2,3,41,2,4,51,2,3,51,2,3,5-

81 79 71 -30 92 93

-48 -23 -23 -28 185 225

2,32,42,52,63,43,5-

(lv3) (1) (2) (2) (4) (all)

1,2,31,2,4lJ2,41,2,31,2,41,3,5-

49 69 78

40

-59 141 141

89

643

731 555 554

545 617 460 660 515 1242

425 498 507 362 1078 1130

352 937 900

730

Phenol: AIoa I

Phenyi acetateg: &xocn, #

Phenol*: Al,,@

Anisole**: AIocirJI

Polar

Low-polarity

COlWnn

34-

(1,3) (194)

1,21,31,4-

(192) 2-

Parent-

(1)

l-

chloro isomer formed

Chlopobenzeneisomer with (in parentheses) positions of substituted group

101

341 72 72

296 299 35 287 51 294

242 252 239 -3 246 255

176 194 185

103

&ca~@

Ankole**:

223

334 237 226

325 331 231 340 249 429

317 333 333 236 419 419

315 414 399

363

618

720 542 549

570 634 494 648 513 999

473 521 530 390 893 905

411 796 759

641

AloRB

97

233 77 79

1% 206 52 198 62 184

161 173 168 27 154 162

127 125 107

63

AIoci$

110

180 145 139

188 199 156 203 173 230

195 209 209 168 235 235

192 232 212

195

AIococrr,~

Deference: polar - low-polarity

WITH HYDROXY, METHOXY AND

Phenyl acetat@: &cocn~ I

INCREMENTAL EFFECTS DUE TO SUBSTITUTION OF ONE CHLORINE ATOM IN CHLOROBENZENES ACETOXY GROUPS, OBTAINED ON LOW-POLARITY AND POLAR CAPILLARY COLUMNS AT 160°C

TABLE IV

R

b

:

Parentoo,o’m-, P-

Isomer formed

SUMMARY

TABLE V

89 -59-12 -34-25 141-243

AIon

Low-polarity

Column

OF THE INCREMENTAL

40 49-108 -30-4 69-110

AloCH, 168 122-154 68-l 13 182-199

&COCH,

EFFECTS PRESENTED

730 352-731 362643 900-1242

AIOH

Polar

IN TABLE IV

103 176-341 -3-101 185-294

A’oCIiJ 363 315340 223-249 399-429

hcocn,

641 41 I-720 390-618 759-999

AI,,

63 127-233 27-97 107-184

GCH,

Polar - low-polarity

195 180-209 110-173 212-235

hcocn3

124

Substitution

I. 0.0.

KORHONEN

of one chlorine atom in chlorobenzenes with an additional group

Table IV and Figs. 4 and 5 show the incremental effects due to the substitution of one chlorine atom in chlorobenzenes with hydroxy, methoxy or acetoxy groups, obtained on low-polarity and polar capillary columns. A summary of the values is presented in Table V. The effects observed are almost the same as presented above, the enhancements being lower as a consequence of the substitution, i.e., AZ = Zfn- 1)c1(isomer formed) - Zncl(benzene). Anisole, phenol and phenyl acetate on low-polarity columns show enhancements of 40, 89 and 168 i.u. relative to chlorobenzene, the values increasing on polar columns to 103, 730 and 363 i.u., respectively. The replacement of an o-chlorine atom with a hydroxy group generally gives rise to a reduction in the retention on the low-polarity columns, as shown in Table IV and Fig. 4. The increments for o-chlorophenols lie in the range -59-12 (352-731) i.u., for the o,o’-isomers -34-25 (362643) i.u. and for the m- and pisomers 141243 (900-1242) i.u., the values on polar columns, given in parentheses, being markedly higher (Tables IV and V). With methoxy substitution the smallest retention enhancements are shown by the o,o’-isomers, the increments on low-polarity and polar columns lying in the ranges - 30-4 and - 3-101 i.u., respectively. With the other isomers enhanced retentions of 49-110 i.u. on low-polarity and 176-341 i.u. on polar columns are observed. Increased retention always occurred on acetoxy substitution and it is apparent that the increments fall into three groups, particularly on polar columns, viz., 1%

Fig. 4. Incremental effects due to the replacement of one chlorine atom in chlorobenzenes with hydroxy, methoxy and acetoxy groups, obtained on low-polarity capillaq columns at MOT (Table IV). (A) Phenol; (0) anisole; (0) phenyl acetate. The numbers indicate the positions of chlorination.

125

GLC ANALYSES. XxX11. WLARcMUM*S

0

p.mt

2

3

4

ISOWER

23

24

25

es

I 24

35

234

235

236

2.5

248

345

2345

234%

235(1

23456

Fig. 5. Effects as in Fig. 4, obtained on polar capillary columns at 160°C (Table IV).

154 (315-340) i.u. for the o-isomers, 68-113 (223-249) i.u. for the o,o’-isomers and 1X2-199 (399429) i.u. for the m- and pisomers on low-polarity and (in parentheses) polar columns, as shown in Table V. Subtraction of the non-polar contributions given in Table IV and particularly the summary of the values presented in Table V show the relatively lower values for o,o’-chloroanisoles and -chlorophenyl acetates and also for some o,o’-chlorophenols compared with the other isomers, or with the data presented in Tables I and II. This is due to the facts that (i) vicinally substituted chlorobenzenes have higher retention times than the other homologues, particularly on the polar columr?, and (ii) an additional group substituted into vicinal1,2,3-tri-, 1,2,3&tetra-, 1,2,3,5-tetra-, pentaand hexachlorobenzenes prevents the interaction of the chlorine atoms, giving rise to smaller retention increments than the substitution producing the other isomers. ACKNOWLEDGEMENTS

Financial support for this work from the Kalle and Dagmar VPlimaa Foundation (Cultural Foundation of Finland), the Medica Corporation Research Foundation, the Alfred Kordelin Foundation and the Academy of Finland is gratefully acknowledged. REFERENCES 1 2 3 4 5 6 7

I. J. I. I. J. I. I.

0. K. 0. 0. K. 0. 0.

0. Korhonen, J. Chromatogr., 298 (1984) 101, and references cited therein. Haken and I. 0. 0. Korhonen, J. Chromarogr., 265 (1983) 323. 0. Korhonen, J. Chromatogr., 315 (1984) 185. 0. Korhonen, J. Chromatogr., 294 (1984) 99. Haken and I. 0.0. Korhonen, J. Chromutogr., 257 (1983) 267. 0. Korhonen, J. Knuutinen and R. Jtiskeliiinen, J. Chromatogr., 287 (1984) 293. 0. Korhonen and J. Knuutinen, J. Chromutogr., 292 (1984) 345.