Intermolecular interactions in some pyridazinium ylides solutions

133

Journal of Molecular Structure, 293 (1993) 133-136 Elsevier Science Publishers B.V., Amsterdam

Intermolecular Interactions in Some Pyridaabium Ylides lolutions Dana Dorohoi and Viorel Holban Spectroscopy Department.University of Iasi,Romania The nature of intermolecular interactions in the solutions of the pyridazinium ylides has been ana1ysed.A relation for the calculation of the visible band frequencies has been established in function of the solvent parameters.

to the heterocycle

l.INTRODUCTION Pyridazinium ylides are amphionic compounds in which the carbonion is covalently bound to the pyridazinium heterocycle positively charged [l-33. The interactions of pyridazinium ylides with solvents are important because of the frequent use "in situul' of the former as starting products cycloaddition reactions for and for preparing some drugs. The electronic absorption spectra of pyridazinium ylides have [2),in the visible domain,a n-z* band with intramolecular charge transfer of the type Yj-Yi from the carbonion

[1,2] Al

T

This band disappears in the solutions containing free protons.It is very sensitive to the solvent nature. P.EXPERIMENTAL PART We have studied the type ylides with Yj pyridazinium radic 1s -RI,-R, and-R, the in Table 1. he values of the

Table 1 Yi pyridazinium ylides Nr.

Yj

‘Rl

1

YI

-C6H5

2

r,

3

y3

4

r,

122-2860/93/$06.00

-C5H4[-CH(CH3)2]P -C6H5

-C5H4[-CH(CH,),]P

‘R2 -COCgH4

‘R3 040,)

P

-H

-COC,H,(-NO,)p

-H

-COCgH5

'COCgH5

-COCgH5

-COCgH5

0 1993 Elsevier Science Publishers B.V. All rights reserved.

134

Table 2 The wave numbers ~(cx?-~>for Y+ ylides I

I

I

I

1.

benzene

19900

19800

19900

19920

2.

toluene

20040

20000

19900

19920

20150

1 19760

1 19690

3. 1 4.

trichloroethylene

1

trichloromethane

20030

dichloromethane

5. I

20010

!

f I

20170 I

Y,

20160

!

I

20160

I

1

20200

20200 I

Y3

Y,

Ylide

!

Y,

I

No.

I

20200 20200

I

6.

monochlorbenzene

20100

20060

19920

20180

7.

phenyl carbinol

20610

20570

21310

21260

8.

1

isobutyl alcohol

I

1

20680

I

1

20830

I

1

21250

I

1

21210

I

9.

methanol

21060

21110

21620

21710

10.

ethanol

20880

20990

21280

21300

11.

1

isoamyl acetate

1

20260

1

20200

1

20100

12.

n-propyl alcohol

20760

20820

21160

13.

n-amyl alcohol

20680

20830

21100

isopropyl alcohol

14. I

15. I

n-butyl alcohol

I

16.

1

20730 I 1

20720

I

methyl acetate

I

1

20850

I

20330

I

1

I 1

21230

I

20270

1

1

20120 21230

1

21160 21100

21080

20760 I 1

1

I 1

21210

I

20230

I

1

20160

I

17.

cyclohexanol

20510

20590

21110

21160

18.

n-butyl acetate

20410

20430

20210

20220

19.

1

ethyl acetate

1

20210

1 I

20310

1 I

20100

1 I

20120 20100

1-bromopropane

20190

20250

20080

21.

pyridine

20210

20190

20100

20260

22.

acetone

20310

20300

20260

20160

23.

acetonitrile 1

24.

1

25. 26.

1

propane 1,2-diol

[

I

nitrobenzene I I

20420

dichloroethane

1

21000

1

I

19900 1 1

20470

I

1

20540

I 1

1

20370

I

1

20290

I

I

19880

1 21970 I 20140

1 21900 I 20200

20510

I t

I t

21030

20220

20220

135

frequencies V(cm-l) in the visible R-X* band maxima is presented in Table 2. 3.RESULT8

AND DISCUSSION8

The processing of the experimental data has been achieved based on a multiple linear regression calculation program [3] using the following solvent parameters: P,=(e-l)/(r+2); P2=MR; P3=kt&; P4= (n2-1)

/ (n2+2)

; Ps=P,-P,

(1)

In (1) E is the electrical permittivity,MR-is the molar refraction,8, represents the chemical shift of the NMR signal for the proton of the -OH group in the pure solvent,k is the number of the -OH groups in the molecules of the protic solvents and n represents the refractive index of solvents. The choice of PI, P2, P4 andP, parameters for the multiple regression has been suggested by the theories on the impact of solvents on the electronic absorption spectra.Taking into account the fact that the parameter P3 points to the uncovering degree of the -OH group proton,we have chosen it for describing the intensity

of the specific interactions between ylides and the protic solvents. A relation of type (2) was established: (2) Llc (cm-l)=co+cIPI+c2P2+c~P~ The relation (2) with the parameters Ci in Table 3, allows expressing with enough precision the frequency in the visible band maximum for the analysed Yj substances. The results of the statistic processing are presented in Table 4. From Table 4 it results that the multiple correlation coefficient R ,does not diminish under 0.9.For the control quantities [41 we obtained bigger values than the critical adequate ones. Out of [5,6] and the data presented in Table 3,it results that in the nonprotic solvents Y1 and Yz ylides take part in the dispersion,while Y, and Y4 participate in the orientation-inductioninteractions. The positive values ofC, coefficient in the case ofY, and Y4 ylides,show the diminution [5] of the electric dipole momentum as consequence

Table 3 The Ci coefficient in the relation (2) No.

II 1.

Ylide 1

c&AC,

I

~&AC,

I

c,+Ac2

r

c3+Ac3

Y,

1 20580+200

-17.4k7.5

103223

2.

Y,

20640+170

-19.7k6.5

114+19

3.

Y,

19870+130

683+351

176+27

4.

Yd

19890+180

406_+277

182+22

136

Table 4

of the intermolecular charge transfer. The sign minus of the C2 coefficient shows the increase of the polarizability of the molecules by and Y2 Y, excitation. For all the solutions of the Y. ylides in the protic the fourth term in solve&s relation (2) is different from zero,which shows the presence of the proton donor-acceptor specific interactions. C3 coefficient is always positive for all pyridazinium ylides.It supports the assertion that the binding energy of the proton donor-acceptor complex between the molecules of protic solvent and those of pyridazinium ylides is bigger in the ground state of complex comparatively with the excited state [7]. This assertion can also be motivated if one accepts the mechanism Yj-Yj'for light absorption [1,2] and the procharge intermolecular tonic transfer being localised on the ylide carbonion [3]. Q.CONCLUSIONS In the solutions of the pyridazinium ylides with nonprotic solvents in function of

the structure of their carbonion,either orientation-inducinteracdispersion tion,or tions appear.There appear specific interactions of the type proton donor-acceptor in the protic solvents. REFERENCES l.I.Zugrsvescu,M.Petrovanu,N Ylid Chemistry Academic London Press, McGraw Hill, (1976). 2.D.Dorohoi,M.Rotariuc,E. Lupu,M.Petrovanu,Mai Van Tri, An.Qt.Univ Iasi Ib,22,p.35,41, 45 (1976). 3.G.Surpsteanu, Alain LaCombier Heterocycles blache 22, 2079, (1984). $.G.Henrion,

A.Henrion,R.

Henrion, Beispiele zur Datenanalyse mit BASIC Programmen, Berlin p.264-282 (1988). Chem.Soc Bull 5.T.Abe. Japan 38,1314 (1965) 39,939 (1966). 6.H.G.BakhshievSpectrospiia mejmoleculiarnXh vzaimodeistvii, Izd.Nauka, Leningrad P* 162, (1976). 7.G.C.Pimente1,A.L. McClellan, The Hydrogen Bond L.Pauling editor, San Francisco,London,chap.4.1.5, (1960).