Res.J.Chem.Sci.___________________________________________Research Journal of Chemical Sciences Vol. 1(3) June (2011)                   ISSN 2231-606X78 AM1 and ESI/MS study of the Fragmentation of 4-Acyl Isochroman-1,3-Diones: Correlation between Electronic charges of Atoms and Fragmentations processesAbdoulaye Djandé, Bintou Sessouma, Lamine Cissé3 Léopold Kaboré  Karifa Bayo, Alphonse Tine and Adama SabaLaboratoire de Chimie Bio Organique et de Phytochimie, UFR-SEA, Université de Ouagadougou, BURKINA FASO Laboratoire de Chimie de Coordination, UFR-SEA, Université de Ouagadougou, BURKINA FASO Laboratoire de Photochimie et d’Analyse, Faculté des Sciences et Techniques, Université Cheikh Anta DIOP de Dakar (Sénégal), BURKINA FASOAvailable online at: 
www.isca.in
(Received 28th April 2011, revised 3nd May 2011, accepted 9th May 2011) Abstract Recently, it has been found a good correlation between the fragmentation processes of coumarins in electronic impact mass spectrometry (eims) and the electronic charges of the atoms of their hydrocarbon skeleton. The same results have been obtained with eims spectra of 4-acyl isochroman-1,3-diones and the electronic  charges of their atoms. In this paper, the analytic method has been applied to ESI/MS mass spectra of a series of 4-acyl ischroman-1,3-diones to verify its reliability and extensibility. The results, which have been described for the very first time, show that fragmentations take place at the level of atoms bearing high positive charge, according to the nature of ionisation projectile. The results are in good agreement with the earliest studies. Keywords: ESI/MS, 4-acyl isochroman-1,3-dione, electronic charges, fragmentation. Introduction 4-Acyl isochroman-1,3-diones are interesting compounds studied in our laboratories. It has been found several properties for these compounds. So, they exhibit fluorescence 1-2 anti-oxydant and anti-bacterial properties among others. Some of their spectral properties, RMN, mass, UV-Visible and reactivity3,7-9 have been described. Their crystal structures are also been investigated10-12.  Recently it has been found a good correlation between the fragmentation of some organic compounds in electronic impact mass spectrometry (eims) and the charges of their atoms performed by AM1 semi empirical method. It has been found that fragmentation processes in eims take place mainly on the level of atoms bearing high negative charge13-15. It is then possible to predict and explain most of their fragmentations using electronic charges of atoms. The same analytic method has been successfully applied to the eims spectra of title compounds16. So, for the very first time, we should like to apply the method using the electronic charges of atoms in the study of fragmentations of title compounds in ESI/MS. So, ESI/MS spectra of a series of 4-acyl isochroman-1,3-diones has been chosen to establish and confirm the reliability of the method and to evaluate its extensibility. Good results have been obtained. Material and Methods Preparation of 4-acyl isochroman-1,3-diones:The title compounds have been prepared as early described by action of acid chlorides or acid anhydrides on homophtalic anhydride (HPA) in the presence of an appropriated base as shown below (scheme 1) ;      
Res.J.Chem.Sci.___________________________________________Research Journal of Chemical Sciences Vol. 1(3) June (2011)                   ISSN 2231-606X79 Scheme-1: Synthesis of 4-acylisochroman-1,3-diones 
O
O
O
RC
O
X
O
O
R
O
O
H
                           HPA                                    X = Cl or OCOR B = pyridine or triethylamine. 1a
: R = CH; 1b: R = C; 1c:  R = C;   1d
: R = -NO4; 1e: R = -ClC4;  1f
: R = -(CHNC4; 1g: R = -CNC.   
 
Recording spectra: ESI/MS mass spectra, described in the below table 1, are obtained with a 3200 QTRAP (Applied Bio systems SCIEX) mass spectrometer apparatus, equipped with an atmospheric pression ionisation source (API). The sample is dissolved in 500L of chloroform and diluted at 1/100 in a 3mM methanolic solution of ammonium acetate. It is then ionized in positive electrospray mode in the follow conditions: electrospray tension (ISV) : 5500V ; Orifice tension (OR) : 20V ; pression of nebulisation gas (air) : 20psi ; debit : 5L/min. The fragmentation spectra are obtained after dissociation induced by collision; collision gas
 
is N ; energy of collision 20eV ; two quadripôles tandem mass analysers. Spectra presented two to six fragments with a significant relative abundance (%�20) characterising their stability. AM1 Calculation of electronic charges: All the electronic charges of atoms are performed by Austin Model 1 (AM) semi empirical method17from “Chem3D Ultra8” software, using a “Pentium 4” computer. Results are reported in tables 2a, 2b and 2c. Results and discussion        The acylated isochroman-1,3-diones 1
 have been obtained by the described method with more than 70% yield. They have been identified by their melting point and by their H, 13C and 17O NMR spectra3,5. General modes of fragmentations of 4-acyl isochroman-1,3-diones Formation of the pseudo molecular ion [M+H]+ The pseudo molecular ion [M+H]+ has been described to be obtained by the follow reaction exposed in scheme 2. It is noticeable that the reaction takes place at the level of heteroatom under SP hybridization (O and O), due to the easiest mobility of p electrons doublets and their best ability to react with acids (scheme 2). Scheme-2: Formation of pseudo-molecular ion 
O
O
O
O
H
R
H+
O
O
O
O
H
R
O
O
O
O
H
R
H
H
                              A                              B Formation of [M +H]  – HO and [R-CO] or [Ar-CO] ions: So, the proton used in the ionisation pathway, react with O or O to give [M+H]+  The reaction leads to [M+H] – HO and R-CO fragments by the following processes:- after protonation of O, the loss of a molecule of water by direct fragmentation leads to     [M+H]  – HO fragment as shown below (scheme 3):   Scheme 3: Formation of [M+H]  – HO 
O
O
O
R
O
H
H+
O
O
O
R
O
H
H
O
O
O
R
MH+    H                                         MH - H1a
: R=CH: m/z = 187;  1b
: R = C: m/z = 201; 1c
: R = C: m/z = 249;  1d
: R = -ClC: m/z = 283 1e
: R = -NO: m/z = 294;  1g:
 R = -CNC: m/z = 274 It is also possible, after formation of the pseudo molecular ions, to obtain a prototropy of this molecular ion as described in scheme 47,9 which then, leads to the formation of acylium fragment (scheme 4) 
Res.J.Chem.Sci.___________________________________________Research Journal of Chemical Sciences Vol. 1(3) June (2011)                   ISSN 2231-606X80 Scheme-4: Formation of acylium fragment 
O
O
O
O
H
R
H+
O
O
O
O
H
H
R
O
O
O
H
O
H
R
O
O
R
O
H
O
H
RC
O
RC
O
Acylium ion
1a
: R = CH3: m/z = 43; 1b
: R = C5   : m/z = 57; 1c
: R = C5: m/z = 105;  1d
: R = pClC: m/z = 139-14; 1e
: R = pNO: m/z = 150;  1f
 R = p(CHNC4 : m/z = 148;   1g
: R = pCNC4: m/z = 130. These fragmentations take place at the level of C11and C. So, according to the nature of the charge of proton, which is the source of ionisation, the fragmentations processes seemed to take place at the level of atoms bearing a high positive charge as 11 and C. Formation of fragment m/z = 145: The formation of this fragment has been found to be particularly interesting. It has been described to be formed by the follow process described in the below scheme 5: Scheme-5: Formation of fragment m/z = 145 
O
O
O
H
O
H
R
O
O
O
H
R
H
O
Rotation
O
O
O
H
O
R
H
O
O
R
H
O
O
H
- CO
O
H
R
H
O
- RH
C
H
O
O
  
O
O
R
H
O
O
H
- CO
O
H
R
H
O
- RH
C
H
O
O
H
O
O
m/z = 145
C
O
O
H
O
O
- RH
O
O
O
H
O
- COThis fragment at m/z = 145 is known as 3-isocoumaryl cation. Its presence in the spectra of most of the compounds is conforming to the
 
synthesis route to isocoumarins by the reaction described by R. N. Usgaonkar and al.. Thus, under treatment of 4-acyl isochroman-1,3-diones by a 80% aqueous solution of sulphuric acid, the reaction lead to the formation of corresponding 3-alkyl isocoumarins. The authors found that when the reaction is run at room temperature, the 3-alkyl 4-carboxy isocoumarin is obtained as majority compound with a little portion of 3-alkyl isocoumarin. However, in high temperature, only the 3-alkyl isocoumarin is obtained, according to the follow scheme 6: Scheme-6: Synthesis of isocoumarins from 4-acyl isochroman-1,3-diones 
O
O
O
O
H
R
RT
O
C
O
O
H
R
O
+
O
R
H
O
H3O+
O
R
H
O
exclusive compoundIn this case of ESI/MS spectrometry, the results are comparables. So the conditions of recording spectra seemed to be very closes to those described by Usgaonkar and al. The mechanism proposed by the authors is reproduced below in scheme 7. It is once, noticeable that the fragmentations obtained are directed by C11, Cand C. These atoms of carbon are bearers of high positive electronic charges. 
Res.J.Chem.Sci.___________________________________________Research Journal of Chemical Sciences Vol. 1(3) June (2011)                   ISSN 2231-606X81 Scheme-7: mechanism of formation of isocoumarin [8,9] 
RO
OHOH
OCOOHRO
OHOR
- CO3-alkyl or aryl              4-carboxy-3-alkyl or aryl isocoumarine                        isocoumarine
OH
O
H
R
O
O
O
O
HO
O
R
H
H
- H
O
O
R
O
HO
Formation of fragment m/z = 117 and 89: These fragments take place from the precedent fragment m/z = 145. The process of its fragmentation is a well known process described to be two successive loss of a molecule of carbon monoxyde6,17,18 to give the tropylium cation m/z = 89. In this process, the fragmentation takes place at the level of C and C which are bearers of the highest positive electronic charge (scheme 8). Scheme 8: Formation of fragment m/z = 117 and 89. 
CHCO
HO
H
m/z = 117 m/z = 89m/z = 145- CO
H
C
O
O
H
O
O
H
However, between the whole fragmentations described above, only the fragmentation leading to the acylium ion is observable in the spectrum of If
. The fragmentations of this compound follow an atypical pathway and will be considered below. Atypical fragmentations of 1fFormation of pseudo molecular ion: 1f [R = (CHNC], has never been studied in mass spectrometry. It is noticeable that this compound 1f has an atypical behaviour in ESI/MS. The nitrogen atom of its amino group has a very significant influence in its behaviour. Due to the presence of the nitrogen atom, it is possible to assume many forms of the pseudo molecular ion as indicated below in scheme 9 and its fragmentations. Scheme-9: Possible forms of pseudo molecular ion. 
O
O
O
O
H
N
CH
H3C
O
O
O
O
H
N
CH
H3C
HH
O
O
O
O
H
N
CH
H3C
H
A
B
                                               C
O
O
O
O
H
N
CH
H3C
H
The lack of the fragments m/z = 292 and 265, materializing respectively the loss of neutral molecules of water (HO) and dimethylamine (CHNH in the spectrum of 1f
, is indicative of non formation of the A and C types of pseudo molecular ions. Only pseudo molecular ion B is then formed, due to its best stability and lead to fragmentations giving the spectrum of 1f
. In the other hand, all the fragments m/z = 145, 117 and 89, observed in all the spectra of the above compounds, are not observables in the spectrum of 1f
. According to the nature of the charge of the hydrocarbon skeleton of this compound, the fragmentation processes will take place at the level of atoms bearing high positive charge as C, , C10, C11, and C15. So the follow fragments are obtained. Their formations can be explained by the below mechanisms. Formation of m/z = 295 and 267 fragments: These fragments derive from the pseudo-molecular ion B. The fragmentations of B lead to fragments stabilized by electron donating effect of the nitrogen atom (scheme 10). 
Res.J.Chem.Sci.___________________________________________Research Journal of Chemical Sciences Vol. 1(3) June (2011)                   ISSN 2231-606X82 Scheme-10: mesomeric forms of pseudo molecular ion B. 
O
O
O
O
H
N
H
  BCH
H3C
O
O
O
O
H
N
H
CH
H3C
CO
O
O
O
H
N
H
CH
H3C
CO
O
O
O
H
N
H
CH
H3C
CO
O
O
O
H
N
H
CH
H3C
CO
O
O
O
H
N
H
CH
H3C
CO
O
O
O
H
N
H
CH
H3C
ED
O
O
C
H
O
O
H
N
CH
H3C
This pseudo-molecular ion is the most stable than the others. It will be the parent peak leading to the formation of the most significant fragments. The first fragment is formed by the loss of a methyl group leading to the fragment [M+H] – 15,   (m/z = 295). The second fragment can be obtained from E as parent peak, after transposition of an atom of hydrogen from one of the methyl groups linked on the nitrogen atom, on the phenyl ring as shown below (scheme 11): Scheme-11: Formation of fragment 267 ([M+H]  – 43) 
O
OH
C
O
O
H
N
CH
H2C
H
O
OH
C
O
O
H
H
H2CN
CH
m/z = 267This transposition of the aliphatic proton is known and described several time18-20 for alkyl and dialkylaminophenyl moieties. In the compound 1f
, the atom C15 is bearer of a relative high positive charge and can control this fragmentation. Formation of fragment m/z = 166 and 148: According to the electronic charge of atoms, the formation of these fragments must take place at the level of carbons C and C11, bearing high positive charge. It is then possible to propose the follow mechanism as an explanation; the process starts from D as parent peak (scheme 12). Scheme-12: Mechanism of formation of fragment m/z = 166 and 148 
C
O
OH
OH
O
N
H3C
H3C
O
1
C
O
OH
OH
O
N
H3C
CH
m/z = 148 (100%)
C
O
OH
O
O
H
N
H3C
H3C
N
CH
CH
1
2
 
C
O
OH
OH
O
N
H3C
CH
N
H3C
CH
HO
OH
N
H3C
CH
HO
OH
m/z = 166
After the prototropy, the formation of the fragments m/z = 148 takes place by simple cleavage of C-C11 bond (way 1). The 1,3-migration of the phenyl group from C11 onto C(way 2) leads to the fragment m/z = 166 by subsequent cleavage of the C-C bond. It is necessary to assume this transfer of the phenyl group20-22 as shown in the above scheme 12 to explain the formation of this fragment m/z = 166. The high positive charge of the atoms of carbon 11 and C, can make possible this transfer between C11 and C. Nevertheless, the process described in scheme 4 for the formation of fragment m/z = 148 remain possible. Formation of fragment m/z = 121: This fragment comes directly from the pseudo 
Res.J.Chem.Sci.___________________________________________Research Journal of Chemical Sciences Vol. 1(3) June (2011)                   ISSN 2231-606X83 molecular ion by two successive cleavages as shown below. The formation of this fragment is controlled by oxonium atom O and carbon atoms  and C10. These atoms of carbon are bearer of positive electronic charge (scheme 13), even if the charge of C10 is weak. Scheme-13: Formation of the fragment m/z = 121 
O
O
H
O
O
H
N
CH
H3C
O
OH
m/z = 121Conclusion In this study, it has been found that the fragmentations of 4-acyl isochroman-1,3-diones in ESI/MS spectrometry / positive electrospray mode, take place mainly at the level of atoms bearing a significant positive charge. So, according to the nature of the charge of ionisation projectile, the fragmentations processes take place mainly at the level of atoms bearing the same type of charge. In eims, it has been observed that fragmentations take place at the level of atoms bearing high negative charge. In this ESI/MS positive electrospray mode ionisation study, most of the important fragmentations take place at the level of atoms bearing high positive charge. It is then possible to predict the fragmentation processes of organic compounds using the electronic charge of the atoms of their hydrocarbon skeleton. The ESI/MS spectrum of a new compound 1f
, has been successfully analysed through this method. In the other hand, the behaviour of most of these compounds in ESI/MS in positive electrospray mode, is very close to their behaviour when they are treated by acid middle. In this case, the compounds are transformed into corresponding 3-alkyl or 3-aryl isocoumarins. In the present ESI/MS positive electrospray mode spectrometry, one of the fragmentations observed, lead to a fragment identified as 3-isocoumaryl cation; except for 1f
. This result suggests that, sometimes, it will be possible to predict the behaviour of an organic compound in acidic condition, by studying its mass spectrum recorded in ESI/MS electrospray positive mode. At last, it will be interesting to study the behaviour of 1f
 in the reaction described by Usgaonkar and al, transforming title compounds into isocoumarins by acidic treatment. Aknowlodgments We are gratefull to Pr. Jean Pierre AYCARD, Pr. Thierry CHIAVASSA and Madame Valerie MONNIER from Université de Provence (Marseille – France) for recording ESI/MS spectra. References 1.  Djandé A., Kaboré L., Saba A. and Aycard J. P., Synthesis and Fluorescence properties of 4-acyl isochroman-1,3-diones, Heterocyclic Comm.24(4), 237 (2008)2.  Djandé A., Kaboré L., Ayard J. P. and Saba A., Fluorescence properties of 4-acyl isochroman-1,3-diones,  Bull. Chem. Soc. Ethiopia, 23(1), 001  (2009)3.  Djandé A., Thèse Unique, UFR-SEA, Université de Ouagadougou Burkina Faso(2008)4. Bationo-Napon B., Thèse de Pharmacien(Diplôme d’Etat), UFR-SDS, Université de   Ouagadougou, Burkina Faso  (2009)5.  Saba A., Sib S. F., Faure R. and Aycard J. P., NMR and AM1 Study of the tautomeric equilibrium of isochroman-1,3-diones, Spectroscopy Letters, 29(8), 1649 (1996)6.  Djandé A., Kaboré L., Aycard J. P. and Saba A., Study of the fragmentation of 4-acyl isochroman-1,3-diones in mass spectrometry, Phys. Chem. News, 31, 125 (2006)7. Schnekenburger J., Acyl derivatives of methylene active dicarbonyl compounds. IV. Acylation of homophtalic anhydride with ethyl chlorocarbonate, Arch. Pharm. 298Bd n°7, 411, (1965)
Res.J.Chem.Sci.___________________________________________Research Journal of Chemical Sciences Vol. 1(3) June (2011)                   ISSN 2231-606X84 8. Nadkarni D. R. and Usgaonkar R. N., A New Synthesis of Tetrahydrocapillarine, Methylglomelline and Oospolactone, Indian  J. Chem.,16B, 320 (1978)9.  Saba A., Thèse d’Etat ès Sciences PhysiquesUniversité de Ouagadougou(1996)10.  Kakou-Yao R., Saba A., Ebby N., Pierrot M. et Aycard J. P., Tautomérie de la 4-(hydroxyphénylméthylène) isochroman-1,3-dione à l’état solide, Acta Crystallogr., C551591 (1999) 11. Kakou-Yao R., Dandé A., Kaboré L., Saba A. and Aycard J. P., Acta Cryst., E63, o4275 (2007)12.  Abou A., Goulizan Bi S. D., Kaboré L., Djandé A., Saba A. and Kakou-Yao R., Crystal structure of 4-(1-hydroxypropyl) isochroman-1,3-dione, Z. Naturforsch.,  64b, 328 (2009)13.  Cissé L., Tine A., Kaboré L.  and Saba A., Mass spectrometry study of coumarins: Correlation between charges of atoms and fragmentations processes, Spectroscopy Letters,  42, 95 (2009)14.  Cissé L., Kaboré L., Tine A. and Saba A., Analysis of fragmentations of coumarins in mass spectrometryusing the electronic charges of atoms, Bull. Chem. Soc. Ethiopia,24(2), 305 (2010) 15.Cissé L., Kaboré L., Saba A.  and Tine A., Study of mass spectra of 4,7-disubstituted coumarins : Correlation between electronic charges of atoms and fragmentations processes, Phys. Chem. News, 53,  101 (2010)16.Djandé A., Sessouma B., Kini F.B., Kaboré L., Bayo K., Guissou P. I. and Saba A., AM1 and electronic impact mass spectrometry study of the fragmentations of 4-acyl isochroman-1,3-diones, Bull. Chem. Soc. Ethiopia, (2011), in press. 17.Dewar M. J. S., Zoebish, E. G., Healy E. F., Stewart J. P. P., AM1 : A new general  purpose quantum mechanical molecular model,  J. Amer. Chem. Soc., 107, 3902 (198518.Silverstein R. M., Webster F.X. and Kiemle D.J. Identification Spectrométrique de Composés Organiques, Ed. de BOECK, (2007)19.Michel A., Thèse de Doctorat ès Sciences, Université de Neuchâtel  (Belgique) 35 (200120.Laure F., Thèse de Doctorat ès Sciences,  Université de Polynésie Française (France) 230 (200521.Qian R., Liao Y-X, Guo Y-L. and Guo H., ESI-FTICR-MS Studies on Gas Phase Fragmentation Reactions of ArPd(PPhI Complexes, J. Amer. Soc. Mass Spectr., 17(11), 1582 (2006)22.Gusten H., Klasinc L., Maric D. and Srzic D. Phenyl group effect on fragmentations of diazoles, oxazoles and thiazoles, phenyl migration in 2,4,5-triphenyloxazole, International J. of Mass Spectrom.Ion Physics, 47, 423, (1983). Structure of 4-acylisochroman-1,3-diones  
O
O
O
O
H
1011
O
O
O
O
H
1011
x
121314151617
13
Res.J.Chem.Sci.___________________________________________Research Journal of Chemical Sciences Vol. 1(3) June (2011)                   ISSN 2231-606X78 Table-1: ESI/MS Mass Spectra of 4-acylisochroman-1,3-diones Table-2a: Electronic charges of atoms of 1 R C C C C C C C C C10 C11
CH 0.414
 
0.426
 
-0.321
 
-0.207
 
-0.149
 
-0.212
 
-0.109
 
-0.175
 
0.050
 
 
0.210
 
CHCH 0.414
 
0.425
 
-0.319
 
-0.206
 
-0.145
 
-0.211
 
-0.110
 
-0.175
 
0.045
 
 0.209
 
 0.414
 
0.423
 
-0.328
 
-0.198
 
-0.157
 
-0.215
 
-0.109
 
-0.185
 
0.034
 
 0.271
 
pClC 0.412
 
0.426
 
-0.315
 
-0.202
 
-0.151
 
-0.214
 
-0.111
 
-0.176
 
0.047
 
 0.265
 
p(CHNC
 
0.414
 
0.428
 
-0.334
 
-0.202
 
-0.151
 
-0.216
 
-0.112
 
-0.181
 
0.054
 
 0.285
 
pNO 0.406
 
0.417
 
-0.240
 
-0.139
 
-0.179
 
-0.086
 
-0.117
 
-0.151
 
0.030
 
 0.364
 
pCNC 0.413
 
0.425
 
-0.300
 
-0.197
 
-0.150
 
-0.209
 
-0.112
 
-0.175
 
-0.038
 
0.247
 
1a
R = CH3 1b
R = C5 1c
R = C66HH551d
R = -NO1e
R =-ClC4 1f
R=-(Me)NC
 
1g
R=-CNC
m/z             %
 
m/z               
%         
 m/z                % m/z                  % 
  
m/z                 % m/z                 % m/z               % 
  
205[M+H]  9.6 
 
219[M+H]   
84.21  
 267[M+H]  
13.55 
312[M+H]    
23.73  
     
303[M+H]     53.57 310[M+H]    11.17 292[M+H]+          57
 
187          13.8 
 
201           10.52  249                 
2    
294             
13.55   
   
285              
3.57          
295                 5.6 274          11.78 
 
177               1 
 
191                  2  205                 1 250                    5 
  
257                  25 267               3.62 264                 1 
 
163           100 
 
173                  3  177                 1 248               6.78 
  
241                 1.8 166                 4.7 248                 1 
 
149        55.17 
163              100
  145          10.16 150                 100 
  
145               37.5 151                     1 246                 1 
 
145        65.52 
159             5.26
 117                  3 145                   44 
  
141                100 
148                100                                  
230                 1  
 
135        17.24 
145           68.42
 105              100 119                   22 
  
117                    1 
  
121               2.35 
145            45.82
 
 
117        10.35 
135            
      1  89              6.78 117                    5 
  
113                    1 
  
107                    1 
130               100
 
 
89            8.62 
117           
       5  77             30.50
 
104                  2.5 
  
89                      1 - 
117             2.35    
 
57          15.52 
 
99                   6  53              3.40 89                       1 - - 
102                  1
 
 
43          32.75 
 
89                   3 - - - - 
89                    1
 
 
29              2.0 
 
57             75.43 - - - - - 
- 
 
39                  3.5
 
- - - - - 
85 
Res.J.Chem.Sci.___________________________________________Research Journal of Chemical Sciences Vol. 1(3) June (2011)                   ISSN 2231-606X79 Table-2b: Electronic charges of atoms of 1            R    C12     C13     C14    C15    C16    C17     O     O     O    O
CH -0.351       -       - - - - -0.301 -0.285 -0.355 -0.307 
CHCH -0.254 -0.349       - - - - -0.300 -0.286 -0.354 -0.307 
 -0,112 -0,136 -0,203 -0,164 -0,199 -0,141 -0.319 -0271 -0.341 -0.299 
pClC -0.107 -0.132 -0.190 -0.057 -0.188 -0.135 -0.294 -0.271 -0.373 -0.306 
P(CHNC
 
-0.180 -0.083 -0.273 0.152 -0.270 -0.091 -0.307 -0.286 -0.363 -0.308 
pNO -0,159 -0,133 -0,144 -0,054 -0.147 -0,132 -0.210 -0.237 -0.292 -0.217 
pCNC -0.085 -0.151 -0.157 -0.007 -0.158 -0.147 -0.297 -0.284 -0.362 -0.299 
Table-2c: Charge of atoms of substituent X       X      Cl N C O O 
      Cl -0,0108 - - - - 
(CHN - -0.383 -0.188 - - 
    
NO
2
 
-
 
0.518
 
-
 
-
0.297
 
-
0.305
 
     CN - -0.061 0.068 - - 
 
86 
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