Effect of para substitution on dissociation of N-phenylbenzenesulfonamides

Article abstract of DOI:10.1135/cccc20041479

The reaction of substituted anilines and benzenesulfonyl chlorides has been used to prepare 49 substituted N-phenylbenzenesulfonamides of general formula 4-X-C₆H₄SO₂NHC₆H₄-Y- 4′. Their purity was checked by elemental analysis. The substituents X and Y include H, CH₃, CH₃O, Cl, Br, CN, and NO₂. The dissociation constants of all compounds were determined by potentiometric titration in methanol, acetonitrile, N,N-dimethylformamide, and pyridine. The obtained dissociation constants, pK_HA, were correlated with various sets of substituent constants. It was found that the effects of substituents X and Y on the dissociation are best described by using the Hammett equation with σ_p constants and the Yukawa-Tsuno equation with σ_p^- and σ_p constants, respectively. This result confirms the direct conjugation of Y substituent with the reaction centre. The explained variability using the additive model was above 96% in all the solvents used. The data also provided information about the transmission effect of the SO₂ group. The average dissociation constants were further processed by the latent variables methods, principal components and conjugated deviations analyses.

Full text of DOI:10.1135/cccc20041479

Dissociation of N-Phenylbenzenesulfonamides
1479
EFFECT OF pa ra SUBSTITUTION ON DISSOCIATION OF
N-PHENYLBENZENESULFONAMIDES
1
2,
3
Martin MANSFELD , Patrik PAŘÍK * and Miroslav LUDWIG
Department of Organic Chemistry, Faculty of Chemical Technology, University of Pardubice,
1
nám. Čs. legií 565, 532 10 Pardubice, Czech Republic; e-mail: martin.mansfeld@seznam.cz,
2
patrik.parik@upce.cz, 3miroslav.ludwig@upce.cz
Received Jun e 13, 2003
Accepted April 4, 2004
Th e reaction of substituted an ilin es an d ben zen esulfon yl ch lorides h as been used to prepare
49 substituted N-ph en ylben zen esulfon am ides of gen eral form ula 4-X-C6H4SO2NHC6H4-Y-4′.
Th eir purity was ch ecked by elem en tal an alysis. Th e substituen ts X an d Y in clude H, CH3,
CH3O, Cl, Br, CN, an d NO2. Th e dissociation con stan ts of all com poun ds were determ in ed
by poten tiom etric titration in m eth an ol, aceton itrile, N,N-dim eth ylform am ide, an d pyridin e.
Th e obtain ed dissociation con stan ts, pKHA, were correlated with various sets of substituen t
con stan ts. It was foun d th at th e effects of substituen ts X an d Y on th e dissociation are best
described by usin g th e Ham m ett equation with σp con stan ts an d th e Yukawa–Tsun o equa-
–
tion with σp an d σp con stan ts, respectively. Th is result con firm s th e direct con jugation of Y
substituen t with th e reaction cen tre. Th e explain ed variability usin g th e additive m odel was
above 96% in all th e solven ts used. Th e data also provided in form ation about th e tran sm is-
sion effect of th e SO2 group. Th e average dissociation con stan ts were furth er processed by
th e laten t variables m eth ods, prin cipal com pon en ts an d con jugated deviation s an alyses.
Keyw ord s: Sulfon am ides; Dissociation con stan t; Substituen t effects; Tran sm ission effect;
Ch em om etrics; Acidity; Ham m ett equation .
Th e validity of th e Ham m ett relation sh ip h as already been verified on a
large n um ber of various substrates in volvin g ben zoic acids, an ilin es, ph e-
n ols, n aph th oic acids, N-ph en ylsulfon ylben zam ides, etc. An oth er in terest-
in g substrate for studies in th is area is N-ph en ylben zen esulfon am ide 1 with
substituen ts at position s 4 an d 4′.
Th e reaction cen tre of th is com poun d (am ide n itrogen atom ) is con -
n ected to two ben zen e rin gs – on e of th em directly an d th e oth er th rough
th e partly isolatin g SO2 group. Th is en ables m on itorin g of two differen t
ways of substituen t affectin g in on e m odel system . It can be presum ed th at
th e X substituen ts will affect th e dissociation con stan t less com pared with
th e Y substituen ts. In addition , th ere exists a possibility th at th e n egative
ch arge of th e con jugated base of N-ph en ylben zen esulfon am ide will be
Collect. Czech. Chem. Commun. (Vol. 69) (2004)
doi:10.1135/cccc20041479

1480
Mansfeld, Pařík, Ludwig:
delocalized by direct con jugation in to th e Y substituen t due to its location
at th e altern atin g para-position in th e ben zen e rin g.
2'
3
5
2
3'
5'
O
S
4
4'
X
7
NH
Y
7'
O
6
6'
1
Y
X
OCH3
1aa
1ba
1ca
1da
1ea
1fa
CH3
1ab
1bb
1cb
1db
1eb
1fb
H
Cl
Br
CN
1af
1bf
1cf
1df
1ef
1ff
NO2
1ag
1bg
1cg
1dg
1eg
1fg
OCH3
CH3
H
1ac
1bc
1cc
1dc
1ec
1fc
1ad
1bd
1cd
1dd
1ed
1fd
1gd
1ae
1be
1ce
1de
1ee
1fe
1ge
Cl
Br
CN
NO2
1ga
1gb
1gc
1gf
1gg
Th is com m un ication is n ot th e first to deal with m easurem en t an d evalu-
ation of dissociation con stan ts of para-substituted N-ph en ylben zen esulfon -
am ide. However, it tries to approach th e problem as system atically as possi-
ble. Earlier papers usually covered sm aller sets of th ese com poun ds or struc-
turally cogn ate on es. Th e dissociation con stan ts foun d are used in th ose pa-
pers as com parison series in studies of tautom eric equilibria1, studies of sub-
stituen t effects on pK of various com poun ds2,3, or th ey are correlated with
kin etic data4. More exten sive in vestigation in th is field is represen ted by
papers of Dauph in an d Kergom ard5–7, wh o used water an d aqueous eth an ol
of various con cen tration s as th e m edia for m easurem en ts of dissociation
con stan ts. An oth er paper of in terest by Javůrková8 deals with N-ph en yl-
ben zen esulfon am ides with substituen ts presen t on ly in th e an ilin e m oiety.
Th e paper9 by Nádvorn ík also sh ould be m en tion ed, sin ce it studies th e
ortho-effect in N-ph en ylben zen esulfon am ide as th e substrate an d form s a
com plem en t to th is study.
Th e ch ief aim of th e presen t work is to com pare th e substituen t effects
from th e two ben zen e rin gs of m odel com poun ds upon th e value of dissoci-
ation con stan ts. Th e paper form s a con tin uation of form er studies dealin g
with various N-ph en ylben zen esulfon am ides8,9
.
Collect. Czech. Chem. Commun. (Vol. 69) (2004)

Dissociation of N-Phenylbenzenesulfonamides
1481
EXPERIMENTAL
Th e 1H an d 13C NMR spectra of th e m odel com poun ds n ot yet described in literature were
m easured on a Bruker AMX 360 apparatus usin g th eir 5% solution s in DMSO-d6 an d th e
ch em ical sh ifts (δ, ppm ) were referen ced to th e solven t sign al. Th e purity of sulfon am ides
was ch ecked by elem en tal an alysis usin g an autom atic an alyser EA 1108 (Fison s). Th e disso-
ciation con stan ts of all th e substan ces at 25 °C in m eth an ol (MeOH), aceton itrile (AN),
N,N-dim eth ylform am ide (DMF), an d pyridin e (Py) were determ in ed by poten tiom etric titra-
tion s usin g TITRALAB 3 autom atic titrator (Radiom eter). Th e m eth od of m easurem en t an d
th e electrode arran gem en t used were th e sam e as in our previous paper10. Each m easure-
m en t was repeated th ree to five tim es. Th e solven ts used (HPLC purity) were addition ally
dried over m olecular sieves.
Syn th eses of In term ediates
4-Cyan oben zen esulfon yl ch loride was prepared from 4-am in oben zon itrile by diazotization
an d decom position of th e diazon ium salt with sulfur dioxide in th e presen ce of cuprous
ch loride (a m odification of kn own procedure11). Yield 72%, m .p. 90–103 °C (lit.12 gives m .p.
110 °C); it was n ot n ecessary to purify th is com poun d for n ext syn th eses.
4-Ch loroben zen esulfon yl ch loride was syn th esized from ch loroben zen e by reaction with
ch lorosulfuric acid (a m odification of kn own procedure13). Yield 81%, m .p. 45.5–47.5 °C
(lit.14 gives m .p. 53 °C).
Syn th eses of Substituted N-Ph en ylben zen esulfon am ides
Th e m odel substan ces were prepared by th e followin g gen eral procedure: an an ilin e deriva-
tive (0.011 m ol) was dissolved in pyridin e (1 m l, 0.0125 m ol) an d ben zen esulfon yl ch loride
(0.01 m ol) was added. Th e reaction m ixture was h eated on boilin g water bath for 5 m in an d
th en m ixed with dilute h ydroch loric acid. Th e crude product was reprecipitated from its so-
lution in aqueous sodium h ydroxide, wh ich was filtered with ch arcoal an d acidified with
h ydroch loric acid. Th en th e product was recrystallized from aqueous eth an ol (th e water con -
ten t varied depen din g on th e particular product).
Th e syn th eses startin g from 4-cyan oben zen esulfon yl ch loride h ad to om it th e reprecipi-
tation from sodium h ydroxide solution sin ce th e CN group is quickly h ydrolyzed to CONH2
in th e alkalin e m edium . Th is fact was con firm ed by both elem en tal an alysis an d NMR spec-
troscopy.
Th e yields, m eltin g tem peratures, an d elem en tal an alyses of seven m odel sulfon am ides
n ot yet described in literature are given below.
1af: Yield 30%, m .p. 188–191 °C. 1H NMR (DMSO-d6): 3.81 s, 3 H (H-7); 7.10 d, 2 H
(H-2′,6′); 7.31 d, 2 H (H-3,5); 7.72 d, 2 H (H-2,6); 7.84 d, 2 H (H-3′,5′). 13C NMR (DMSO-d6):
55.9, 105.5, 114.9, 118.6, 119.0, 129.3, 130.8, 133.9, 142.7, 163.1. For C14H12N2O3S (288.3)
calculated: 58.32% C, 4.20% H, 9.72% N, 11.12% S; foun d: 58.28% C, 4.22% H, 9.53% N,
10.83% S. 1ef: Yield 30%, m .p. 186–188 °C. 1H NMR (DMSO-d6): 7.31 d, 2 H (H-3′,5′);
7.74 d, 2 H (H-2′,6′); 7.80 s, 4 H (H-2,3,5,6). 13C NMR (DMSO-d6): 106.1, 118.9, 119.1, 127.7,
129.0, 132.9, 134.0, 138.6, 142.2. For C13H9BrN2O2S (337.2) calculated: 46.31% C, 2.69% H,
23.70% Br, 8.31% N, 9.51% S; foun d: 46.82% C, 2.78% H, 24.15% Br, 8.21% N, 8.75% S.
1fa: Yield 31%, m .p. 142.5–144.5 °C. 1H NMR (DMSO-d6): 3.71 s, 3 H (H-7′); 6.85 d, 2 H
(H-3′,5′); 7.02 d, 2 H (H-2′,6′); 7.87 d, 2 H (H-3,5); 8.06 d, 2 H (H-2,6). 13C NMR (DMSO-d6):
Collect. Czech. Chem. Commun. (Vol. 69) (2004)

1482
Mansfeld, Pařík, Ludwig:
55.2, 114.5, 115.2, 117.6, 124.1, 127.5, 129.3, 133.3, 143.5, 157.0. For C14H12N2O3S (288.3)
calculated: 58.32% C, 4.20% H, 9.72% N, 11.12% S; foun d: 58.09% C, 4.19% H, 9.71% N,
10.93% S. 1fd : Yield 30%, m .p. 174–180.5 °C. 1H NMR (DMSO-d6): 7.15 d, 2 H (H-2′,6′);
7.36 d, 2 H (H-3′,5′); 7.94 d, 2 H (H-3,5); 8.10 d, 2 H (H-2,6). 13C NMR (DMSO-d6): 115.8,
117.8, 122.5, 127.7, 129.2, 129.6, 133.8, 136.2, 143.4. For C13H9ClN2O2S (292.8) calculated:
53.34% C, 3.10% H, 12.11% Cl, 9.57% N, 10.95% S; foun d: 53.30% C, 2.77% H, 12.25% Cl,
9.44% N, 10.85% S. 1fe: Yield 53%, m .p. 205–210 °C. 1H NMR (DMSO-d6): 7.11 d, 2 H
(H-2′,6′); 7.45 d, 2 H (H-3′,5′); 7.96 d, 2 H (H-3,5); 8.05 d, 2 H (H-2,6). 13C NMR (DMSO-d6):
115.9, 117.3, 117.8, 122.7, 127.7, 132.5, 133.7, 136.7, 143.4. For C13H9BrN2O2S (337.2) cal-
culated: 46.31% C, 2.69% H, 23.70% Br, 8.31% N, 9.51% S; foun d: 46.35% C, 2.62% H,
24.29% Br, 8.35% N, 9.65% S. 1fg: Yield 60%, m .p. 193–194.5 °C. 1H NMR (DMSO-d6):
7.37 d, 2 H (H-2′,6′); 8.06–8.20 m , 6 H (H-2,3,5,6,3′,5′). 13C NMR (DMSO-d6): 116.0, 117.4,
118.5, 125.4, 127.5, 133.8, 143.0, 143.1, 143.5. For
C13H9N3O4S (303.3) calculated:
51.48% C, 2.99% H, 13.85% N, 10.57% S; foun d: 51.65% C, 2.98% H, 13.80% N, 10.53% S.
1gf: Yield 45%, m .p. 193–196°C. 1H NMR (DMSO-d6): 7.33 d, 2 H (H-2′,6′); 7.74 d, 2 H
(H-3′,5′); 8.13 d, 2 H (H-2,6); 8.41 d, 2 H (H-3,5). 13C NMR (DMSO-d6): 106.5, 118.8, 119.4,
125.1, 128.6, 134.0, 141.8, 144.6, 150.4. For C13H9N3O4S (303.3) calculated: 51.48% C,
2.99% H, 13.85% N, 10.57% S; foun d: 51.74% C, 3.02% H, 13.94% N, 10.72% S.
RESULTS AND DISCUSSION
Th e values of dissociation con stan ts of th e substrates are given as average
values pKHA (with stan dard deviation s) in Table I. In order to exam in e th e
effect of m edium on th e dissociation process, four solven ts were selected
for th e titration . Th e ch oice respected th e requirem en t for usin g curren t ti-
tration m edia an d rough coverage of th e basic types of solven ts: am ph i-
protic m eth an ol, dipolar aprotic protoph obic aceton itrile, dipolar aprotic
protoph ilic N,N-dim eth ylform am ide, an d pyridin e wh ich addition ally h as
basic properties. Th e substituen ts ch osen can be classified as on es with out
an y distin ct reson an ce effect (CH3, H, Cl, Br), th ose with positive reson an ce
effect (OCH3), an d th ose with n egative reson an ce effect (NO2, CN). Th is
ch oice appeared to be represen tative sam ple of substituen ts in our recen t
studies.
Mean values of th e dissociation con stan ts m easured were subjected to
calculation s by th e m eth ods with laten t variables. Th e m ain goal of th ese
calculation s is to isolate sign ifican t in form ation s in cludin g in data m atrices
via obtain in g in dividual laten t variable vectors. Both m eth ods used, prin -
cipal com pon en ts an alysis (PCA)15 an d con jugated deviation s an alysis
(CDA)16, gave com parable results. Th erefore, m ain ly on ly th e results from
PCA will be discussed h ere. Th e m ean values of dissociation con stan ts,
pKHA, were arran ged in to a m atrix A com prisin g 4 colum n s (solven ts) an d
49 rows (substrates). Th e calculation on th is m atrix revealed two laten t
variables as statistically sign ifican t. Th e first laten t variable t1A explain ed
Collect. Czech. Chem. Commun. (Vol. 69) (2004)

Dissociation of N-Phenylbenzenesulfonamides
1483
TABLE I
Mean values of dissociation con stan ts (pKHA) an d th eir stan dard deviation s (s) of substituted
N-ph en ylben zen esulfon am ides 1 in in dividual solven ts at 25 °C
1
MeOH
AN
DMF
Py
1aa
1ab
1ac
1ad
1ae
1af
1ag
1ba
1bb
1bc
1bd
1be
1bf
1bg
1ca
1cb
1cc
1cd
1ce
1cf
13.58(0.02)
13.47(0.02)
13.28(0.03)
12.75(0.02)
12.66(0.03)
11.47(0.02)
11.09(0.06)
13.52(0.04)
13.46(0.11)
13.21(0.03)
12.63(0.08)
12.64(0.02)
11.36(0.08)
10.97(0.01)
13.50(0.04)
13.38(0.02)
13.17(0.02)
12.61(0.03)
12.52(0.02)
11.22(0.03)
10.76(0.05)
13.12(0.01)
13.11(0.01)
12.85(0.02)
12.20(0.01)
12.08(0.03)
10.81(0.04)
10.37(0.03)
13.29(0.07)
13.05(0.04)
12.84(0.05)
12.23(0.02)
12.08(0.05)
10.81(0.03)
10.42(0.05)
12.06(0.02)
11.85(0.06)
11.65(0.02)
11.13(0.06)
11.12(0.05)
10.04(0.06)
9.74(0.02)
23.99(0.09)
23.62(0.10)
23.71(0.08)
22.75(0.13)
22.61(0.11)
21.20(0.02)
20.39(0.04)
23.86(0.11)
24.21(0.03)
23.87(0.12)
22.58(0.14)
22.81(0.04)
20.99(0.13)
20.39(0.04)
23.36(0.07)
23.14(0.12)
23.42(0.10)
22.57(0.02)
22.47(0.03)
20.72(0.05)
19.93(0.04)
22.85(0.04)
22.83(0.14)
22.52(0.01)
21.77(0.10)
21.50(0.11)
20.23(0.13)
19.38(0.02)
23.13(0.11)
23.01(0.10)
22.63(0.06)
21.81(0.06)
21.79(0.10)
20.10(0.01)
19.56(0.03)
22.74(0.09)
22.41(0.01)
22.05(0.03)
21.17(0.04)
21.13(0.08)
19.42(0.12)
18.70(0.03)
22.59(0.01)
21.96(0.11)
21.63(0.12)
20.79(0.13)
20.67(0.11)
19.31(0.06)
18.41(0.02)
14.45(0.16)
14.30(0.07)
13.78(0.07)
13.06(0.07)
12.88(0.01)
11.53(0.08)
10.52(0.06)
14.15(0.11)
13.57(0.14)
13.34(0.11)
12.67(0.04)
12.68(0.13)
11.37(0.05)
10.25(0.06)
13.21(0.09)
13.13(0.03)
12.89(0.07)
12.53(0.07)
12.41(0.13)
11.45(0.08)
10.11(0.05)
12.97(0.04)
12.71(0.04)
12.69(0.08)
12.35(0.03)
12.17(0.08)
11.17(0.04)
9.50(0.06)
11.83(0.07)
12.06(0.13)
11.41(0.05)
10.55(0.07)
10.09(0.10)
8.46(0.12)
7.48(0.05)
11.98(0.02)
11.77(0.04)
11.36(0.18)
10.40(0.07)
10.27(0.07)
8.32(0.15)
7.65(0.14)
11.78(0.17)
11.51(0.06)
10.99(0.02)
9.94(0.02)
10.01(0.04)
7.85(0.01)
6.98(0.04)
11.10(0.03)
10.58(0.14)
10.30(0.14)
9.82(0.11)
9.96(0.07)
7.32(0.02)
6.46(0.07)
10.91(0.03)
10.78(0.12)
10.49(0.12)
9.19(0.02)
9.37(0.08)
7.79(0.03)
7.02(0.10)
10.12(0.05)
9.83(0.01)
9.42(0.02)
8.47(0.03)
8.41(0.01)
6.61(0.03)
5.83(0.01)
9.85(0.03)
9.57(0.05)
9.11(0.06)
8.11(0.04)
8.05(0.01)
6.27(0.02)
5.35(0.08)
1cg
1d a
1d b
1d c
1d d
1d e
1d f
1d g
1ea
1eb
1ec
1ed
1ee
1ef
13.42(0.05)
13.10(0.11)
12.81(0.08)
12.02(0.05)
12.09(0.08)
10.68(0.12)
9.51(0.08)
1eg
1fa
12.67(0.04)
12.47(0.01)
12.19(0.07)
11.58(0.03)
11.52(0.03)
10.26(0.04)
8.97(0.06)
1fb
1fc
1fd
1fe
1ff
1fg
1ga
1gb
1gc
1gd
1ge
1gf
1gg
12.56(0.03)
12.44(0.02)
12.08(0.07)
11.47(0.00)
11.40(0.01)
10.08(0.02)
9.67(0.01)
12.59(0.06)
12.36(0.04)
12.01(0.05)
11.25(0.04)
11.12(0.05)
9.60(0.05)
8.80(0.06)
Collect. Czech. Chem. Commun. (Vol. 69) (2004)

1484
Mansfeld, Pařík, Ludwig:
98.24% of variability of th e source m atrix; th e secon d laten t variable de-
scribin g an oth er 0.99% variability was at th e lim it of statistical sign ifican ce.
It can be stated th at th e values of th e laten t variable t1A obtain ed express
th e com bin ed effect of both substituen ts, X an d Y, on th e dissociation of
th e m odel substrates free from furth er effect affectin g th e exten t of disso-
ciation , particularly th e solven t effect. Plottin g of th ese data again st th e
substituen t con stan ts17 σp provides a better view of relation sh ips between
substituen ts an d th e dissociation con stan ts. Th e depen den ce of t1A vs
σp(X) presen ted in Fig. 1 sh ows 7 descen din g series of 7 poin ts each : in each
serie th ere is always a n on -variable Y substituen t an d varyin g X. Hen ce we
sh ould actually observe seven Ham m ett straigh t lin es. However, it can be
seen , e.g., th at th e poin ts for X = OCH3 (σp = –0.28) h ave a lower t1A value
th an expected from th e lin ear relation sh ip: th is substituen t sh ows th us a
weaker don or effect, approach in g th at of X = CH3 (σp = –0.14). Also, it is
obviously n ot correct to con sider com parable substituen t effects for X = Cl
an d Br (both σp = 0.22). Clearly, th e poin ts correspon din g to th is substitu-
tion do n ot overlap in th e picture, wh ich in dicates sligh tly differen t effects
of Cl an d Br substituen ts from th e X position . Figure 2 sh ows th e depen d-
en ce of t1A vs σp(Y), i.e. each of th e descen din g serie expresses 7 com -
poun ds with a con stan t X substituen t an d varyin g Y. Com pared with Fig. 1,
it can be seen th at th e in dividual Ham m ett straigh t lin es h ave larger slopes
an d th eir distan ces at th e t1A axis are sm aller. Th is result correspon ds to
th e presum ption th at th e sen sitivity of th e m odel substrates to Y substitu-
tion is h igh er an d th at to X substitution is lower. Moreover, it can be seen
1.0
t1A
0.1
–0.8
–1.7
–0.2
0.1
0.4
0.7
σ (X)
p
FIG. 1
Depen den ce diagram of t1A vs σp(X). Y = ᮀ OCH3, × CH3, ᭹ H, ᭺ Cl, ꢀ Br, ᭝ CN, ᭿ NO2
Collect. Czech. Chem. Commun. (Vol. 69) (2004)

Dissociation of N-Phenylbenzenesulfonamides
1485
th at all th e poin ts with Y = NO2 (σp = 0.81) sh ow lower t1A values th an ex-
pected from th e lin ear depen den ce, wh ich correspon ds with th e idea of di-
rect con jugation between th e substituen t an d reaction cen tre; depen din g
on th e exten t of th is con jugation , th e substituen t con stan t of n itro group
–
gen erally assum es th e values up to σp (1.25).
In order to furth er evaluate th e relation sh ip between th e type of substitu-
tion an d th e exten t of dissociation , th e pKHA values were arran ged in to two
sim ilar m atrices. In th e m atrix XY, con tain in g 7 rows an d 28 colum n s, th e
rows represen t X substituen ts an d each colum n represen ts a substituen t
Y–solven t com bin ation . Th e m atrix YX of th e sam e dim en sion s was ar-
ran ged an alogously: th e rows represen t various Y substituen ts, an d th e col-
um n s represen t various substituen t X–solven t com bin ation s. Th e PCA cal-
culation on m atrix XY revealed two laten t variables as statistically sign ifi-
can t, first (t1XY) describin g 93.18% variability an d secon d (t2XY) describ-
in g an oth er 3.17% variability of th e source m atrix. Th e obtain ed vector
t1XY expresses th e substituen t effect of X substituen ts. Th e CDA calcula-
tion on th e sam e m atrix sh owed th at th e secon d laten t variable h as a h igh
value for X = CN an d m an ifests itself in all th e seven colum n s for MeOH. In
m eth an ol, it is possible to observe a h igh er acidity of derivatives with X =
CN com pared with th ose with X = NO2, wh ich is un usual. Hen ce it can be
presum ed th at th e secon d variable in m atrix XY will probably describe th is
ph en om en on .
Th e PCA calculation on YX m atrix gave two statistically sign ifican t laten t
variables t1YX an d t2YX, describin g 98.80 an d 0.68% variability of th e
1.0
t1A
0.1
–0.8
–1.7
–0.2
0.1
0.4
0.7
σ (Y)
p
FIG. 2
Depen den ce diagram of t1A vs σp(Y). X = ᮀ OCH3, × CH3, ᭹ H, ᭺ Cl, ꢀ Br, ᭝ CN, ᭿ NO2
Collect. Czech. Chem. Commun. (Vol. 69) (2004)

1486
Mansfeld, Pařík, Ludwig:
source m atrix, respectively. Th e obtain ed vector t1YX expresses substituen t
effects of Y substituen ts. Th e distin ctly h igh est con tribution of th e secon d
laten t variable is in th e colum n DMF, X = Cl. Th e ph ysical m ean in g of th is
secon d laten t variable was n ot foun d; probably it is caused by h igh er vari-
ability of data just in th is colum n . Th e values of vectors of th e in dividual
laten t variables, t1XY, t2XY, t1YX, t2YX, are presen ted in Table II. To
m ake th e picture clearer an d com parison s of substituen t effects from X an d
Y position s easier, th e t1XY, t1YX vectors were tran sform ed to t1XY*,
t1YX* by assign in g th e value of 0 to th e substituen t H, an d th e resultin g
values were given with opposite sign s (see Table II).
–
Th e correlation s of t1XY an d t1YX vs σp, vs σp , an d vs σI, σR (lit.17) were
–
calculated. Relation s t1XY vs σp (r = 0.9974) an d t1YX vs σp (r = 0.9951)
were foun d as th e best correlation s. Th is result in dicates th e m an ifestation
of direct con jugation between Y substituen t an d th e reaction cen tre, too.
Th e dissociation con stan ts m easured were correlated with various sets of
substituen t con stan ts to fin d a m odel describin g th e dissociation as close as
possible. Followin g m odels were tested:
1. pK = pK0 – ρXσp – ρYσp, Ham m ett m odel with substituen t con stan ts σp
for both n uclei
–
2. pK = pK0 – ρXσp – ρYσp , Ham m ett m odel with substituen t con stan ts σp
–
for X substituen ts an d substituen t con stan ts17 σp for Y substituen ts
3. pK = pK0 – ρXσP6 – ρYσP6, Ham m ett m odel with substituen t con stan ts
σP6 adjusted from processes in n on -aqueous m edia18
4. pK = pK0 – ρIXσI – ρRXσR – ρIYσI – ρRYσR, Taft m odel with separated in -
ductive (I) an d m esom eric (R) effects of substituen ts17
TABLE II
Values of vectors of laten t variables from PCA calculation s on m atrices XY an d YX
Vector
OCH3
CH3
H
Cl
Br
CN
NO2
t1XY
t2XY
t1YX
t2YX
1.1530
1.0350
1.0100
–0.3343
0.9960
0.4989
0.8657
–0.7604
0.5604
–1.0690
0.6596
–0.0966
–1.3550
0.1027
0.8115
–0.0301
–0.1717
0.0502
0.5887
–1.1950
1.2750
–1.0530
1.4010
–1.3880
–0.2137
–1.6350
–1.5180
–0.1886
t1XY*
t1YX*
0.5929
0.3504
0.4356
0.2061
0
0
–0.6570
–0.5569
–0.5303
–0.6094
–1.7554
–1.7126
–1.9484
–2.2946
Collect. Czech. Chem. Commun. (Vol. 69) (2004)

Dissociation of N-Phenylbenzenesulfonamides
1487
TABLE III
Regression ch aracteristics of regression m odels 1–5
ρIX (s)
ρRX (s)
ρIY (s)
ρRY (s)
pK0 (s)
r (s)
R (s)
ρX (s)
ρY (s)
Solven t Model
MeOH
1
2
3
4
5
12.90
(0.02)
1.37
(0.04)
2.52
(0.04)
–
–
–
–
–
–
–
–
–
–
0.984
(0.197)
13.02
(0.02)
1.38
(0.04)
1.89
(0.03)
0.986
(0.186)
12.88
(0.02)
1.53
(0.06)
2.85
(0.06)
0.974
(0.254)
12.99
(0.03)
–
–
1.76 (0.05) 3.26 (0.05)
1.58 (0.07) 2.87 (0.07)
0.989
(0.165)
12.97
(0.02)
1.38
(0.03)
2.19
(0.05)
–
–
0.48
(0.06)
0.989
(0.164)
AN
1
2
3
4
5
22.94
(0.03)
1.75
(0.06)
3.39
(0.06)
–
–
–
–
–
–
–
–
–
–
0.980
(0.293)
23.10
(0.03)
1.76
(0.05)
2.56
(0.04)
0.984
(0.264)
22.94
(0.03)
2.02
(0.08)
3.84
(0.08)
0.976
(0.324)
23.23
(0.05)
–
–
2.42 (0.08) 4.45 (0.08)
1.63 (0.10) 3.77 (0.10)
0.986
(0.245)
23.05
(0.03)
1.76
(0.05)
2.91
(0.08)
–
–
0.54
(0.08)
0.987
(0.244)
Py
1
2
3
4
5
10.73
(0.03)
2.12
(0.06)
4.06
(0.06)
–
–
–
–
–
–
–
–
–
–
0.988
(0.275)
10.91
(0.03)
2.12
(0.05)
3.04
(0.04)
0.990
(0.254)
10.71
(0.04)
2.41
(0.08)
4.61
(0.08)
0.981
(0.347)
10.89
(0.04)
–
–
2.76 (0.07) 5.25 (0.07)
2.34 (0.09) 4.65 (0.09)
0.993
(0.211)
10.84
(0.02)
2.12
(0.04)
3.53
(0.07)
–
–
0.48
(0.05)
0.993
(0.211)
DMF
1
2
3
4
5
13.05
(0.03)
1.55
(0.07)
3.11
(0.07)
–
–
–
–
–
–
–
–
–
–
0.969
(0.341)
13.20
(0.03)
1.56
(0.06)
2.36
(0.04)
0.979
(0.283)
13.03
(0.04)
1.77
(0.09)
3.53
(0.09)
0.962
(0.378)
13.02
(0.07)
–
–
1.85 (0.10) 3.97 (0.10)
1.99 (0.14) 3.71 (0.14)
0.972
(0.325)
13.18
(0.03)
1.56
(0.06)
2.53
(0.09)
–
–
0.74
(0.10)
0.979
(0.279)
Collect. Czech. Chem. Commun. (Vol. 69) (2004)

1488
Mansfeld, Pařík, Ludwig:
–
5. pK = pK0 – ρXσp – ρY[σp + r(σp – σp)], additive m odel presum in g X sub-
stituen ts to act accordin g to th e Ham m ett relation sh ip with substituen t
con stan t σp an d Y substituen t to act accordin g to th e Yukawa–Tsun o rela-
tion sh ip, wh ere r describes th e exten t of m esom eric effects19.
In m odels 1–5 subscripts X, Y correspon d accordin gly to effects of X or Y
substituen ts. Th e results of regression s are presen ted in Table III. Wh en
evaluatin g th e quality of regression m odels by th e correlation coefficien ts
(R) an d residual stan dard deviation s (s), we can see th at th e worst result was
provided by m odel (3) despite th e fact th at th e σP6 substituen t con stan ts
were adjusted specially for n on -aqueous m edia. In MeOH, AN, an d Py th e
resultin g order of success of th e m odels is 3 > 1 > 2 > 4 an d th e best is
m odel 5; in DMF th e order is on ly sligh tly differen t: 3 > 1 > 4 > 2, th e best
bein g 5. Hen ce th e best m odel for describin g th e dissociation processes of
th e substrates studied turn ed out to be th e additive m odel presum in g th e
action of X substituen ts accordin g to th e Ham m ett relation sh ip an d th at
of Y substituen ts accordin g to th e Yukawa–Tsun o relation sh ip. Th e result
sh ows larger ability of Y substituen ts to stabilize con jugated base of m odel
substrate th rough larger delocalization in com parison with th e ability of X
substituen ts an d agrees with th e con clusion drawn from th e treatm en t of
data by th e m eth ods with laten t variables.
Th e lower values for ρX reaction con stan ts, as com pared with ρY, foun d in
all th e solven ts con firm th e presum ption th at th e substrate is less sen sitive
to th e substituen ts in th e rin g con n ected with th e reaction cen tre via th e
SO2 group, h en ce th is group acts by its tran sm ission effect, wh ich can be
quan tified on th e basis of th e ratio of reaction con stan ts ρX/ρY (tran sm is-
sion factor) from m odel 5. Its values in th e in dividual solven ts are 0.63
(MeOH), 0.60 (AN), 0.60 (Py), 0.62 (DMF). Th e tran sm ission of substituen t
effects th rough sulfon yl group (substituen ts of type X) th us attain s rough ly
60% of th e exten t of tran sm ission of effects from type Y substituen ts. Th e
param eter r in regression m odel 5 appeared to be statistically sign ifican t in
all th e solven ts. Th is con firm s th e direct con jugation between th e reaction
cen tre an d Y substituen ts, in particular NO2 an d CN substituen ts, stabiliz-
in g th e con jugated base of N-ph en ylben zen esulfon am ide. Th e values of re-
action con stan ts ρ of all th e regression m odels also quan tify th e ability of
solven t to stabilize th e con jugated bases of sulfon am ides. Th e lowest values
of ρ are foun d in MeOH an d in crease in th e order DMF, AN, Py. Hen ce pyri-
din e is th e worst solven t for stabilization of con jugated bases of m odel sub-
strates, an d th e substituen t effects in th is solven t are th e m ost distin ct as it
is seen from th e h igh est values of th e reaction con stan ts.
Collect. Czech. Chem. Commun. (Vol. 69) (2004)

Dissociation of N-Phenylbenzenesulfonamides
1489
CONCLUSIONS
Th e study of acid-base properties of a coh eren t set of 4,4′-disubstituted
N-ph en ylben zen esulfon am ides in four organ ic solven ts sh owed th at th e
com bin ed effect of both substituen ts h as an additive ch aracter. Com pared
with th e effects of Y substituen ts, th e effects of X substituen ts actin g
th rough th e sulfon yl group are weaken ed by th e tran sm ission effect of th is
group, wh ich can be quan tified by a tran sm ission coefficien t of 0.60. For
th e regression m odels tested, th e substituen t effects on th e m odel substrates
are best described by th e additive m odel describin g th e beh aviour of sub-
stituen ts on th e basis of th e Ham m ett relation sh ip an d th at of Y substitu-
en ts on th e basis of th e Yukawa–Tsun o relation sh ip. In th is way it was
foun d out th at direct con jugation of substituen t Y with th e reaction cen tre
operates in th e stabilization of con jugate bases of m odel substrates. For th e
acid-base processes, th e best solvatin g effect is exh ibited by m eth an ol an d,
on th e oth er h an d, due to worse solvation ability of pyridin e, th e substi-
tuen t effects are m ost distin ct in th is solven t.
The authors thank the Ministry of Education, Youth and Sports of the Czech Republic (project
CI MSM 253 100 001) for financial support.
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Collect. Czech. Chem. Commun. (Vol. 69) (2004)