Tautomerism of 1,3,4-thiadiazole. Part 1 - Biblioteka UMCS

ANNALES

U N I V E R S I T A T I S MARIAE C U R I E - S K Ł O D O W S K A

LUBLIN —POLONIA

VOL. L/LI.7 SECTIO AA 1995/1996 School of Medicine, Lublin

LEOKADIA STRZEMECKA *

Tautomerism of 1,3,4-thiadiazole. Part I

Tautomeria 1,3,4-tiadiazolu. I

INTRODUCTION

Theoretically 5R-2R’ -amino-1,3,4-thiadiazole system a) may exist in its tautomeric modifications of 3H-5R-2R’-imino-l,3,4-thiadiazole b) and 3H-2R- 5R ’-imino-l,3,4-thiadiazole c), (Scheme 1).

* Chair and Department of Organic Chemistry, Pharmaceutical Faculty, Akademia Medyczna, 20-081 Lublin, ul. Staszica 6.

G. Komis has reported [1] about the presence of the amino and imino forms a), b) of 2-amino-l,3,4-thiadiazoles and that the tautomeric equilibrium is influ­

enced by the substituents both at the exocyclic nitrogen atom and in the 5-position of 1,3,4-thiadiazole ring.

During the studies on the * H NMR spectra of 5-substituted-2- cinnamylamino-1,3,4-thiadiazole [2], a signal of NH group at various chemical shifts has been observed. This fact may suggest the differences in the structure of 5-substituted-2-cinnamylamino-1,3,4-thiadiazole . These data induced us to examine the structure of 5-substituted-2 -cinnamylamino- 1,3,4-thiadiazole more exactly. There are no reports on this subject in the literature.

RESULTS AND DISCUSSION

The aim of the present paper was to describe the structure of 5-(2’ -pyri- dyl-)-2-allyl-(cinnamyl-)amino- 1,3,4-thiadiazole a) and its tautomeric modifica ­ tions b), c) (Scheme 2).

Scheme 2.

1a,b,c R' = -CH2-CH=CH2 2a,b,c R’ = -CH_-CH=CH-CcHc

--- z □ □

The tautomeric modifications of 5-(2 ’ -pyridyl-)2-allylamino-1,3,4-

thiadiazole la), lb), 1c) were obtained by the cyclization of N'-(allyl-

thiocarbamyl-)-N3-phenyl-2-picolineamidrazone (methods I — IV) with:

Tautomerism of 1,3,4-thiadiazole. Part 1

83

I. diluted 3.6% ethanolic solution of HC1 at room temperature II. diluted 3.6% hydrochloric acid at room temperature

III. concentrated 36% hydrochloric acid at room temperature IV. boiling concentrated 36% hydrochloric acid

or by condensation of N 3-phenyl-2-picolineamidrazone dihydrochloride and allylisothiocyanate (methods V,VI) in:

V. boiling anhydrous ethanol VI. boiling N,N-dimethylformamide.

The tautomeric forms of 5-(2 ’-pyridyl-)-2-cinnamylamino-1,3,4-thiadiazole 2a), 2b), 2c) were obtained by the cyclization of N'-(cinnamyl-thiocar bamyl-)N 3-phenyl-2-picolineamidrazone [2] (methods VII; VIII) with:

VII. boiling diluted 3,6% hydrochloric acid

VIII. concentrated 36% hydrochloric acid at room temperature

or by condensation of N 3-phenyl-2-picolineamidrazone dihydrochloride and cinnamylisothiocyanate [2] (methods IX, X) in:

IX. boiling anhydrous ethanol X. boiling N,N-dimethylformamide.

In the 'H NMR spectra of the tautomeric modifications of 5-(2’-pyridyl-)-2- allylamino-1,3,4-thiadiazole la), lb), 1c) the chemical shifts of the signals were ranged as follows:

method spectrum method spectrum

No No

I I 8 8.594-(-0.005) V V 8 8.589-(-0.033)

II II 8 8.58O-(-O.O33) VI VI 8 8.598-(-0.033) III III 8 8.598-(-0.033) VI VI, 8 7.317-0.033 IV IV 8 8.603-(-0.028) VI VI4 8 7.233-0.033

In the 'H NMR spectra of the tautomeric modifications of 5-(2’-pyridyl-)2-

cinnamylamino-1,3,4-thiadiazole 2a), 2b), 2c) the chemical shifts of the signals

were ranged as follows:

method spectrum method spectrum No No

VII VII 8 8.580-0.042 IX IX 8 8.570-(-0.033) VIII VIII 8 8.547-0.019 X X 8 8.570-(-0.005) VIII VIII5 8 13.64-0.000

In the * H NMR spectra of products la), lb), le), 2a), 2b), 2c) obtained by the methods I-X, spectra I-X, VII5 the signals of the protons of allyl, cinnamyl, pyridyl substituents as well as of NH group of 1,3,4-thiadiazole have been re­

corded. In the 'H NMR spectra of products la), lb), 1c) obtained by the meth ­ ods VI, spectra VI3, VI4 the signals of NH group of 1,3,4-thiadiazole ring have only been recorded.

The 'H NMR spectra of products la), lb), 1c), 2a), 2b), 2c) contain signals confirming the presence of unsaturated groups -CH2-CH=CH 2, -CH 2-CH=CH- -C 6 H 5 as well as of the pyridyl substituent (Tables 1, 3). In the 'H NMR spec­

trum of products la), lb), 1c) obtained by the method V, spectrum V there are present double signals of a(6 ’ H) y(4 ’H) ß(5’ H) ß(3 ’H) proton and suggest the presence of the following mesomeric structures of the pyridine ring, Scheme 3.

In the ‘ H NMR spectra of compounds labc), 2abc) obtained by the methods I-X there appear the signals of the protons Hc Hd of allyl-(cinnamyl-) substitu­

ents at various chemical shifts values and support the presence of the structures la de lb de lcde, 2afg 2b fg 2c fg , Schemes 4, 5, respectively.

The chemical shifts values of the protons Hc H d are ranged as follows:

§ 3.999-4.079 (method I, spectrum I) 8 4.003-4.083 (method II,VI, spectra n,VI) S 4.003^4.088 (method III, IV, spectra III,IV) 5 4.003-4.088 (method V, spectrum V)

1 a de 1 bde 1 C d e

8 4.163—4.224 (method VIII, spectrum VIII) 8 4.182-4.252 (method IX, spectrum IX) 8 4.196-4.257 (method X, spectrum X) 8 4.210-4.266 (method VII, spectrum VII)

2afg2bfg2cfg

Tautomerism of 1,3,4-thiadiazole. Part 1

85

Scheme 3.

S 8,387 - 8,345 (6’H)

^8^23 -8,143 (4’H)

<$7,838 - 7,646 (5’H)

JNX HC 0 C HC ® c

h !1

CH CH

58,589-8,514 (6’H)

57,838-7,646 (5’H)

$7,397-7,143 (3’H)

'CH

3 8,589 - 8,514 (6’H)

S 8,223 - 8,143 (4’H) S 7,838-7,646 (5’H)

£■7,397 - 7,143 (3’H)

• - p orbitals - electron pair

@ - negative charge

@ - positive charge

Scheme 4.

• - p orbitals - electron pair sp2, sp3 - orbitals

Tautomerism of 1,3,4-thiadiazole. Part I

87

Scheme 5.

structure

- p orbitals - electron pair sp, sp2 - orbitals

The chemical shifts values of the protons Hc Hd of allyl and cinnamyl sub­

stituents of the structures 1 a de 1 b de 1 cde , 2af g 2bf g 2Cfg, Schemes 4, 5, in the range of

8 3.999 —4.088 and 8 4.163-4.266, respectively, point to the differences in the

hybridization of the atomic orbitals of the exocyclic nitrogen atom 2N(5N) of

1,3,4-thiadiazole ring.

The chemical shifts values of the protons He Hd in the range of 5 3.999- 4.088 support sp 3 or sp2 hybridization of the nitrogen atom 2N(5N) of the structures lad lb d lcd and laelbe lce , respectively, Scheme 4. An electron pair of the exocyclic nitrogen atom 2N(5N) occupy sp 3 or sp2 orbital of the structures

lad lbdlcd and laelb e lce , respectively. In the structures lb dlcd and lb elc e the second sp3 or sp 2 orbital of the nitrogen atom 2N(5N), respectively, may be occupied by one electron.

The chemical shifts values of the protons Hc Hd in the range of 8 4.163- 4.266 confirm sp 2 or sp hybridization of the atomic orbitals of the exocyclic nitro­

gen atom 2N(5N) of the structures 2af2bf2Cf, 2a g 2b g2cg, respectively, Scheme 5.

In the structures 2af g 2bf g 2cfg an electron pair of the nitrogen atom 2N(5N) occu­

pies 2p orbital. Due to the presence of an electron pair on 2p orbital of the nitro ­ gen atom 2N(5N) of the structures 2afg 2bf g 2cfg, Scheme 5 , the chemical shifts values of the protons H c H d of the cinnamyl substituent are shifted to the lower field than those of allyl one of the structures 1 ade 1 b de 1 c de, Scheme 4. In the structures 2b f 2cf and 2bg2cg, Scheme 5, the sp “ or sp orbitals of the nitrogen atom 2N(5N) that do not participate in the creation of the bond may be occupied by one electron.

In the structures lad lb d lc d , 2af2b f 2c f , Schemes 4, 5, respectively, there oc ­ cur sp 3 hybridization of orbitals of the carbon atom 3”C. Then the nitrogen and carbon atoms 2N(5N) 3 ”C create 8 bond. In the structures laelbelc e, 2ag2bg 2c g, Schemes 4, 5, the carbon atom 3 ” C shows sp 2 hybridization, thus the nitrogen and carbon atoms 2N(5N) 3 ”C may create 5 or л bond.

The same range of the chemical shifts values of the protons H c H d of allyl substituent of the structures lad lb dlcd and laelb elc e 8 3.999-4.088 may suggest that 2p orbital both of 2N(5N) and 3” C of the structures lae lb elce may be occu­

pied by one electron and may create 8 or л bonds between these atoms.

The analogous values of the chemical shifts of the protons H c Hd of cinna­

myl substituent of the structures 2af 2b f 2cf and 2ag2bg2cg 5 4.163-4.266 point that one of 2p orbitals of 2N(5N) of the structures 2ag 2b g2cg is occupied by an electron pair. The second 2p orbital of 2N(5N) and 2p orbital of 3 ”C, each of them occupied by one electron, may create 8 or л bond between these atoms.

The small differences in the chemical shifts values of the protons He Hd of allyl, cinnamyl substituents of the structures both I a de I b dc lc dc and 2a fg 2bfg2cfg suggest the differences in the polarization of the bond of the nitrogen and carbon atoms 2N(5N) 3 ”C.

Since exocyclic nitrogen atom 2N(5N) of 1,3,4-thiadiazole ring may show

sp3, sp 2 or sp hybridization then the nitrogen and carbon atoms 2N(5N), 2C(5C)

Tautomerism of 1,3,4-thiadiazole. Part I

89

may create single or double bonds. Due to the possible interactions of 2p orbi ­ tals of 2C(5C), 2N(5N) in the molecules of the studied systems

Iae2afglbe2bfglce 2cfg one can expect the mesoionic forms Ih 2h, li 2i, Ij 2j, re­

spectively, Scheme 6.

Scheme 6.

Uli 1Ы111

2h 2i 2i R' = -CH2-CH=CH-C6H5 , R = J,-pyridyl

In the 'H NMR spectra of products labc, 2abc obtained by the methods I-X there are present the signals of NH group in the range of Ö 13.64 (-0.033) and support the presence of various mesomeric forms of these tautomeric modifica­

tions abc. The chemical shifts values and the intensities of the signals of NH group are collected in Tables 2, 4.

The chemical shifts values of NH group in the range of § 13.64-3.562 point to the lack of the interactions of 2p orbitals of the nitrogen atoms 3N 4N of the 1,3,4-thiadiazole ring in the mesomeric modifications of the tautomeric forms abc. The chemical shifts values of the proton of NH group in the range of 5 3.412 (-0.033) suggest the presence of the interactions of 2p orbitals of the nitrogen atoms 3N 4N of the 1,3,4-thiadiazole ring in the mesomeric forms of the tautomeric structures abc.

EXPERIMENTAL

The [H NMR spectra were measured with a Tesla BS 677A spectrometer

(100MHz with T.F.) in CDC1 3 at room temperature with TMS as the internal

standard. Chemical shifts are given in the Ô scale. Melting points were uncor ­

rected.

N1-(Allyl-thiocarbamyl-)-N3-phenyl-2-picolineamidrazone was the new compound. It was obtained by means of a method previously described [3]. M.p.

145-147 °C (EtOH, 70.9% yield).

Analysis:

ForCl6H17 N 5 S (311.402) Calcd.: 22.5% N, 61.8% C, 5.5% H Found.: 21.8% N, 61.6% C, 5,0% H

5-(2 ’ -Pyridyl-)2-allylamino-l,3,4-thiadiazole la, 3H-5-(2 ’ -pyridyl-)2-allylimino-l,3,4-thiadiazole lb and 3PI-2-(2 ’ -pyridyl-)5-allylimino-l ,3,4-thiadiazole 1c

Method 1

5mmole of Nl-(allyl-thiocarbamyl-)N3 -phenyl-2-picolineamidrazone in lOmmole of 3.6% ethanolic solution of HC1 was left for 48 hrs at room tem­

perature. The solvent was removed. The crude residue was boiled with 100cm ’ of 4% NaOH. The insoluble product was filtered off, washed with water and crystallized from ethanol-water mixture. M.P. 156-158 °C, 1.0g (91.7% yield).

Analysis:

ForC10 H 10N 4S (218.278) Calcd.: 25.7% N Found.: 25.3% N

Method 11

5mmole of Nl -(allyl-thiocarbamyl-)N3 -phenyl-2-picolineamidrazone in lOmmole of 3.6% hydrochloric acid was left for 48 hrs at room temperature.

The reaction mixture was poured into 15cm 3 of water and neutralized with an aqueous ammonia. The crude product was filtered and boiled with 100cm3 of 4% NaOH. The precipitate was filtered off, washed with water and crystallized from ethanol-water. M.p. 158-160 °C, 1.0g (91.7% yield ).

Analysis:

ForC10 H 10N 4S (218.278) Calcd.: 25.7% N

Found: 24.8% N

Tautomerism of 1,3,4-thiadiazole. Part I

91

Method III

5mmole of N'-(allyl-thiocarbamyl-)N3-phenyl-2-picolineamidrazone in 25cm 3 (0.25mole) of 36% hydrochloric acid was left for 48hrs at room tem­

perature. The reaction mixture was poured into 50cm3 of water and neutralized with an aqueous ammonia. The precipitate was filtered off, washed with water and crystallized from water. M.p. 156-157 °C, 1.0g (91.7% yield).

Analysis:

For Cl0Hl0N4 S (218.278) Calcd.: 25.7% N, 55.0% C 4.6% H

■ Found: 25.0% N 55.3% C 4.5% H

Method IV

5mmole of Nl-(allyl-thiocarbamyl-)N ’ -phenyl-2-picolineamidrazone in 25cm3 (0.25mole) of 36% hydrochloric acid was refluxed for 12hrs. After cool ­ ing the reaction mixture was poured into 100cm' of water and neutralized with an aqueous ammonia. The precipitate was filtered off and boiled with 100cm ’ of 4% NaOH. The insoluble product was filtered, washed with water and crystal­

lized from ethanol-water mixture. M.p. 158-160 °C, 0.9g (82.5% yield ).

Analyssis:

For C IOH 1O N 4S (218.278) Calcd.: 25.7% N Found: 24.9% N

Method V

lOmmole of N 3 -phenyl-2-picolineamidrazone dihydrochloride and lOmmole of allylisothiocyanate in 20cm3 of anhydrous ethanol was refluxed for 20 hrs.

The solvent was distilled off. The residue was boiled with 100cm3 of 4% NaOH.

The precipitate was filtered off, washed with water and crystallized from etha­

nol-water mixture. M.p. 135-136 °C, 0.8g (36.7% yield).

Analysis: :

For C10 H

0 N4S (218.278) Calcd.: 25.7% N

Found: 25.3% N

Method VI

lOmmole of N 3-phenyl-2-picolineamidrazone dihydrochloride and lOmmole of allylisothiocyanate in 25cm3 of N,N-dimethylformamide was refluxed for 5 hrs. The solvent was distilled off. The residue was washed several times with water. The crude product was crystallized from ethanol-water mixture. M.p.

153-155 °C, 0.7g (32.1% yield).

For Cl0 H10 N 4S (218.278) Calcd.: 25.7% N Found: 25.4% N

REFERENCES

[1] Korni s G., Comprehensive Heterocyclic Compounds, vol. 6, 545-577, ed. A.R. Ka- tritzky, W.C. Rees, Pergamon Press, London 1984.

[2] S t r z e m e с к a L., Polish J. Chem., 64, 157, (1990).

[3] Barnikow G., Abraham W., Z. Chem., 5, 183, (1969).

STRESZCZENIE

Na podstawie widm 'H NMR 5-(2’-pirydylo-)2-allilo-(cynamylo-)amino 1,3,4-tiadiazolu stwierdzono obecność tautomerycznych Struktur abc oraz ich polarnych form. Przesunięcia che­

miczne protonów grupy -N-CH2- podstawników allilowego i cynamylowego wskazują na różnice w hybrydyzacji orbitali atomowych egzocyklicznego atomu azotu. Otrzymano 5-(2’-pirydylo-)2- alliloamino-1,3,4-tiadiazol.

Tautomerism of 1,3,4-thiadiazole. Part I

93

T ab le

S p ec tr al d at a

ł5/( »^3

\ -- z

N—НЭ

-< o >

НЭ-НЭ

5 8 .5 9 4 -5 8 .5 1 9 IH a 5 8 .2 3 2 -5 8 .1 4 3 IH y 5 7 .8 4 7 -5 7 .6 7 4 IH ß 5 7 .3 3 6 - 5 7 .2 0 0 IH ß 5 8 .5 8 0 -5 8 .5 3 7 IH a 5 8 .2 3 7 -5 8 .1 4 8 IH y 5 7 .8 4 7 -5 7 .6 7 4 IH ß 5 7 .3 3 6 -5 7 .2 0 0 IH ß 5 8 .5 9 8 -5 8 .5 3 7 IH a 5 8 .2 3 7 -5 8 .1 4 8 IH y 5 7 .8 4 7 -5 7 .6 7 4 IH ß 5 7 .3 3 1 -5 7 .1 9 5 IH ß

—

—

-r

5 4 .0 7 9 - 5 3 .9 9 9 2 H 5 4 .0 8 3 - 5 4 .0 0 3 2 H 5 4 .0 8 8 - 5 4 .0 0 3 2 H

II X о

1

5 6 .1 0 1 - 5 5 .7 7 8

5 6 .1 0 6 -5 5 .7 8 2

5 6 .1 1 1 -5 5 .7 8 7

'L T о

СЧ

5 5 .4 5 8 -5 5 .1 9 6 2 H 5 5 .4 6 3 -5 5 .1 9 6 2 Н 5 5 .4 7 7 -5 5 .1 8 2 2 H

S p ec tr u m N o

— g

T ab le

- co n ti n u ed

tr,

8 8 .6 0 3 -5 8 .5 2 8 IH a 5 8 .2 4 2 -5 8 .1 5 2 IH y 5 7 .8 5 2 -5 7 .6 8 3 IH ß 5 7 .3 4 1 -5 7 .2 0 4 IH ß 5 8 .5 8 9 -5 8 .5 1 4 IH a 5 8 .3 8 7 -5 8 .3 4 5 IH a 5 8 .2 2 3 -5 8 .1 4 3 IH y 5 8 .0 7 7 -5 7 .9 7 4 IH y 5 7 .8 3 8 -5 7 .6 4 6 IH ß 5 7 .3 9 7 -5 7 .1 4 3 IH ß 5 8 .5 9 8 -5 8 .5 2 3 IH a 5 8 .2 2 8 -5 8 .1 3 8 IH y 5 7 .8 5 2 -5 7 .6 7 8 IH ß 5 7 .3 3 6 -5 7 .2 0 0 IH ß

г-ï

с<

с с

«

ОС ОС с

«

5 4 .0 8 8 - 5 4 .0 0 8 2 H 5 4 .0 8 3 - 5 4 .0 0 3 2 H

m

5 6 .1 1 1 -5 5 .7 8 7

5 6 .1 0 1 -5 5 .7 7 8

5 6 .1 0 6 -5 5 .7 8 2

(N О'ï

ОСчс

«

С' ОС

« 5 5 .4 6 8 -5 5 .1 7 7 2 H 5 5 .4 8 2 -5 5 .1 9 6 2 H

IV

V I

Tautomerism of 1,3,4-thiadiazole. Part I

95

T ab le 2 . S p ec tr al d at a

_________________________ N H _______________________________

I

S p ec tr u m N o

oo

1_______

y u

5 7 .2 3 3 (2 H ) 5 7 .1 2 0 (3 .0 3 H ) 5 7 .0 3 5 (0 .8 0 2 H )

r-

V I

5 7 .3 1 7 (0 .7 4 H ) 5 7 .2 5 6 (0 .3 4 H ) 5 7 .2 3 3 (2 H ) 5 7 .1 2 5 (2 .0 9 H ) 5 7 .0 4 0 (0 .7 8 6 H )

40

1_______

V I

5 8 .5 9 8 - 5 8 .5 2 3 0 .1 H 5 8 .2 2 8 -5 8 .1 3 8 0 .1 7 2 H 5 7 .8 5 2 -5 7 .6 7 8 0 .1 4 H 5 7 .3 3 6 -5 7 .2 0 0 0 .5 2 2 H

in _>

Tf in СП Tf 40 CH 1П cn —; 05 40 —;

00,—<00,—(00,—

Ю~ю£бО~сО£Ю£Ю^

1 cn IO Ich | in Im 1 ci OOOOOOCNOC-Ocn—<O>in

m en cn O oo en

00 00 00 00

60 60 60 CO 60 60

\_______

IV

5 8 .2 4 2 -5 8 .1 5 2 0 .0 7 H 5 7 .8 5 2 -5 7 .6 8 3 0 .1 3 H 5 7 .3 4 1 -5 7 .2 0 4 0 .4 6 H

cn >—

5 8 .5 9 8 -5 8 .5 3 7 0 .2 3 H 5 8 .2 3 7 -5 8 .1 4 8 0 .1 8 H 5 7 .8 4 7 - 5 7 .6 7 4 0 .2 5 H 5 7 .3 3 1 -5 7 .1 9 5 0 .4 1

CN 1—

5 8 .5 8 0 -5 8 .5 3 7 0 .0 8 H 5 8 .2 3 7 -5 8 .1 4 8 0 .1 H 5 7 .8 4 7 - 5 7 .6 7 4 0 .1 8 H 5 7 .3 3 6 -5 7 .2 0 0 0 .4 3 H

’“i >—«

5 8 .5 9 4 -5 8 .5 1 9 0 .3 8 H 5 8 .2 3 2 -5 8 .1 4 3 0 .3 8 H 5 7 .8 4 7 - 5 7 .6 7 4 0 .4 3 H 5 7 .3 3 6 -5 7 .2 0 0 0 .9 H

T ab le 2 . - c o n ti n u ed

oo

8 4 .0 1 8 (0 .1 9 2 H ) 8 3 .9 9 9 (0 .2 0 0 H ) 8 3 .9 0 5 (0 .8 8 6 H ) 8 3 .4 0 7 (0 .7 5 9 H ) 8 3 .2 9 9 (0 .6 7

!

8 4 .0 1 8 (0 .1 9 H ) 8 3 .9 9 9 (0 .1 8 3 H ) 8 3 .9 1 0 (0 .3 2 6 H ) 8 3 .9 8 1 (0 .3 1 8 H ) 8 3 .6 2 3 (0 .0 7 H ) 8 3 .5 8 1 (O .1 3 7 H ) 8 3 .5 6 2 (0 .1 4 3 H ) 8 3 .4 1 2 (0 .4 8 0 H ) 8 3 .3 0 4 (0 .4 6 6 H ) 8 3 .2 0 6 (0 .0 9 H )

8 6 .6 3 2 (1 H ) 8 6 .1 0 6 -8 5 .7 8 2 0 .0 3 H 8 5 .4 8 2 -8 5 .1 9 6 O .3 3 8 H 8 4 .0 8 3 - 8 4 .0 0 3 0 .6 6 2 H 8 0 .2 4 4 (0 .2 2 3 H ) 8 0 .0 3 3 (0 .3 2 7 H ) 8 0 .0 0 0 (6 .2 5

8 -0 .0 3 3 (0 .4 4 6 H )

МП

8 6 .6 8 3 (1 .1 4 2 H ) 8 5 .4 6 8 -8 5 .1 7 7 0 .9 H 8 4 .0 8 8 -8 4 .0 0 8 1 .3 5 9 H 8 0 .2 3 5 (0 .6 0 2 H ) 8 0 .0 2 8 (0 .6 5 4 H ) 8 0 .0 0 0 (9 .5 3

8 -0 .0 3 3 (0 .5 6 4 H )

8 6 .5 0 0 ( 1 .0 0 9 H ) 8 6 .1 1 1 -8 5 .7 8 7 0 .0 3 H 8 5 .4 8 2 -8 5 .1 8 6 0 .2 4 H 8 4 .0 8 8 -8 4 .0 0 3 0 .3 7 H 8 2 .1 7 3 (0 .3 7 H )

8 0 .2 3 9 (0 .1 6 7 H ) 8 0 .0 3 8 (0 .0 6 3 H ) 8 0 .0 0 5 (1 .3 8 H ) 8 -0 .0 2 8 (0 .0 7 6 H )

8 6 .6 8 3 (1 H ) 8 6 .1 6 7 (0 .3 7 H ) 8 6 .1 1 1 -8 5 .7 8 7 0 .0 1 9 H 8 5 .4 7 7 -8 5 .1 8 2 0 .2 6 H 8 4 .0 8 8 - 8 4 .0 0 3 0 .2 H 8 0 .2 4 4 (0 .1 3 1 H ) 8 0 .0 3 3 (0 .1 1 6 H ) 8 0 .0 0 0 (2 .1 7 H ) 8 -0 .0 3 3 (0 .0 9 9 H )

CN

8 6 .6 7 4 (1 H ) 8 6 .1 6 2 (0 .0 4 5 H ) 8 6 .1 0 6 -8 5 .7 8 2 0 .0 7

8 5 .4 6 3 -8 5 .1 9 6 0 .3 H 8 4 .0 8 3 - 8 4 .0 0 3 0 .4 H 8 0 .0 3 3 (0 .0 5

8 0 .0 0 0 (1 .1 5 H ) 8 -0 .0 3 3 (0 .0 3 6 H )

—’

8 6 .6 5 7 (1 H ) 8 6 .1 0 1 -8 5 .7 7 8 0 .5 3 H 8 5 .4 5 8 -8 5 .1 9 6 0 .7 3 8 H 8 4 .0 7 9 - 8 3 .9 9 9 0 .8 2 2 H 8 0 .0 2 8 (0 .1 1 H ) 8 -0 .0 0 5 (2 H )

Tautomerism of 1,3,4-thiadiazole. Part 1

97

T ab le 3 . S p ec tr al d at a

-< o >

5 8 .5 8 0 -5 8 .5 3 3 IH a 8 8 .1 7 6 -5 8 .0 9 6 IH y 5 7 .8 9 0 -5 7 .6 7 4 IH ß 0 7 .4 4 4 -5 7 .2 4 2 IH ß 8 8 .5 4 7 -5 8 .5 0 0 IH a 5 8 .1 4 3 -5 8 .0 6 3 IH y 5 7 .7 9 6 -5 7 .6 2 7 IH ß 5 7 .4 3 0 -5 7 .1 9 0 IH ß

SH9O---

-

*

■

5 7 .4 4 4 - 5 7 .2 4 2 5 H 5 7 .4 3 0 -5 7 .1 9 0

5 H

— C H = C H —

cn

5 6 .6 6 0

5 6 .4 3 0 -8 6 .1 5 3

5 6 .6 2 2

5 6 .4 1 6 -5 6 .1 4 4

ZE О Z

CM

8 4 .2 6 6 -8 4 .2 1 0 2 H

CM CC ЧО

Ю 1 CM CM CO

ec tr u m N o

—

V II II IA

oo

T ab le 3 . - c o n ti n u ed 5 8 .4 8 IH a 5 8 .0 8 IH y 5 7 .6 4 IH ß 5 7 .2 8 IH ß 5 8 .5 7 0 -5 8 .5 1 9 IH a 5 8 .1 6 2 -5 8 .0 8 2 IH y 5 7 .8 2 9 -5 7 .6 5 5 IH ß 5 7 .4 4 8 -5 7 .2 0 9 IH ß 5 8 .5 7 0 -5 8 .5 2 3 IH a 5 8 .1 6 2 -5 8 .0 8 2 IH y 5 7 .8 3 8 -5 7 .6 6 9 IH ß 0 7 .4 4 8 -5 7 .2 3 3 IH ß

5 7 .2 8 0 5 H 5 7 .4 4 8 - 5 7 .2 0 9 5 H 5 7 .4 4 8 - 5 7 .2 3 3 2 H

5 6 .7 2 -5 6 .1 2 2 H 5 6 .6 4 1 -5 6 .1 4 4 2 H 5 6 .6 4 6 -5 6 .1 3 4 2 H

СЧ

5 4 .2 2 Н 5 4 .2 5 2 -5 4 .1 8 2 2 H 5 4 .2 5 7 -5 4 .1 9 6 2 H

—'

V II I

X1—t ^X

Tautomerism of 1,3,4-thiadiazole. Part I

99

T ab le 4 . S p ec tr al d at a

T ab le 4 . - c o n ti n u ed

IT)

5 6 .8 0 5 (0 .3

5 4 .2 5 7 -5 4 .1 9 6 0 .1 3 4 H

£ £ £ £ £ £ £

IT) Tt r c X

—' cc cc o n < 1

о о о о оф Г" ОС чО О 40 ОС mо

оо о\ оч сс чо сч о

•п сг сч сч о о О о ф ф ф о

wo OO wo wo WO

’ф

5 6 .8 0 1 (O .3 5 3 H ) 5 4 .2 5 2 -5 4 .1 8 2 0 .4 3 0 H 5 0 .5 8 7 (0 .1 6 2 Н ) 5 0 .4 9 8 (0 .1 0 5 Н ) 5 0 .2 4 9 (0 .7 8 3 Н ) 5 0 .0 7 5 (0 .1 З З Н ) 5 0 .0 3 3 (0 .8 5 2 Н ) 5 0 .0 0 0 (1 7 .3 1 6 Н ) 5 -0 .0 3 3 (2 .4 0 6 Н )

cc

5 6 .7 2 -5 6 .1 2 0 .7 5 H 5 4 .2 (0 .5 H )

3 3 3 3 3 чО IC . СЧ О О''J 00 Ml 5? ° о о о 60 ОО 60 WO

СЧ

5 6 .7 8 2 (0 .4 0 2 H ) 5 6 .4 1 6 -5 6 .1 4 4 0 .3 1 H 5 4 .2 2 4 -5 4 .1 6 3 0 .7 3 H 5 2 .1 4 5 (0 .0 1 6 )H 5 0 .4 8 8 (0 .0 3 4 Н ) 5 0 .2 2 5 (0 .2 7 Н ) 5 0 .0 6 6 (0 .1 1 5 Н ) 5 0 .0 1 9 (0 .2 8 3 Н )

—

5 6 .8 1 5 (0 .4 8 H ) 5 6 .6 6 0 (0 .1 2 H ) 5 6 .4 3 0 -5 6 .1 5 3 O .8 3 H

1 ЧС ЧС n

«

H to 5 0 .6 0 1 (О .1 8 3 Н ) 5 0 .5 0 7 (0 .1 2 5 Н ) 5 0 .2 5 3 (0 .3 4 4 Н ) 5 0 .2 3 9 (0 .1 7 1 Н ) 5 0 .0 4 2 (0 .5 2 Н )