88 (1969) RECUEIL 891

547.239.21 : 542.943: 546,881.4'131 THE OXIDATION OF METHYL CYANIDE

BY VANADIUM(1V) CHLORIDE

BY

Miss. C. A. A. VAN DRIEL and W. L. GROENEVELD (Laboratorium voor Anorganische Chemie, Rijksuniversiteit, Postbus 75, Leiden)

The reaction products of Vc14 and excess CH3CN have been characterized by several methods. The main oxidation product is 2-methyl-4,6-bis(trichloro- methyl)-1 ,3,5-triazine.

Introduction In several instances organic solvents behave as reducing agents with

respect to transition-metal halides e.g., pyridine 273, y-picoline 3, bi- pyridyl 3, 1,IO-phenanthroline 3, aryl cyanides 4 and alkyl cyanides 4-9.

The reductions of some metal chlorides found in excess methyl cyanide are :

CH3CN vcl4 --f VC13(CH3CN)3,, 4 and

CH3CN FeC13 + [Fe(CH3CN)6]2+[FeC14-]~ 8 (only partial reduction)

In the same way, other oxidizing chlorides, C0C13, MoC15, WCl.5, wc15 and ReC15, give CoClz(CH3CN)z 5 , MoCI~(CH~CN)Z 6 ,

WCI~(CH~CN)Z 6 , WC14(CH3CN)z and ReC14(CH3CN)z 4 , respectively. In these cases the organic oxidation products have never been isolated;

the evolution of HC1 has been detected in many cases 6 , 7 9 1 0 . Because of

R. A. Walton, Quart. Rev. 19, 126 (1965). R. E. McCarley, B. G. Hughes, J . C . Boatman and B. A. Torp, Advan. Chem. Ser. 37, 243 (1963). M. Allblut, K. Feenan and G. W. A. Fowles, J. Less-Common Metals 6, 299 (1964). G. Rouschias and G. Wilkinson, Chem. Commun. 1967, 442. A. P. Zuur, Thesis, k i d e n 1961.

0 E. A. Allen, B. J . Brisdon and G. W. A. Fowles, J. Chem. SOC. 1964, 4531. 7 M . W. Duckworth, G . W. A. Fowles and R. A. Hoodles, ibid. 1963, 5665.

J. Reedijk and W. L. Groeneveld, Rec. Trav. Chim. 87, 1293 (1968). W. Schneider and A. v. Zelewsky, Helv. Chim. Acta 46, 1848 (1963).

lo G. Rouschias and G. Wilkinson, J. Chem. SOC. A 1968, 489.

892 Miss C. A . A . van Driel and W. L. Groeneveld

the fact that one chlorine atom is lost by the metal chloride it was suggested that the cyanide might be chlorinated and that the reaction might involve free radicals 6* 7 p 1 0 .

Recently Rouschias and Wilkinson l o isolated an organic chloro-com- pound from such a reaction. After the reaction of ReC15 with CHsCN, they filtered the product from ReC14(CH3CN)2 and extracted the liquid with petroleum ether. This extract was concentrated under vacuum and a yellow oil was obtained.

The empirical formula Cg, sH7NCls given by the authors, corresponds neither with the molecular weight found, nor with the analytical results.

In the infrared spectrum of this oil a band at 746 cm-1 (Y (C-Cl)) was present.

We have now studied this redox process for the system VC14-CH3CN.

Experimental Methyl cyanide was purified by fractional distillation from calcium hydride in a nitrogen

atmosphere. Petroleum ether (40-60") was purified as described by Voger 11. Vch was prepared by passing a stream of chlorine over metallic vanadium (- 25 g)

at - 400' and as soon as the VC14 was formed (- 100 g) it was distilled in a chlorine atmosphere and collected in dry CH3CN (- loo0 ml). This solution gave a dark purple- brown sludge and a brown solution. After a few days the colour of the residue turned green.

The solution was extracted several times with petroleum ether. The petroleum ether was completely removed from the extract by distillation. A light yellow oil (about 25 ml) remained, which became darker with increasing bath-temperature. This extract was never heated above 100" in order to prevent decomposition.

After a few days this oil yielded crystals melting at 93-94". Crystals with the same infrared spectrum, but melting at 96" could be obtained when the residue was treated with cold petroleum ether. After a month the oil had solidified, and in this way about 2 g of white crystals could be obtained.

The petroleum ether distilled from the extract (fraction b.p. 40-50") formed two layers in the receiver. It could be concluded from the infrared spectra that the upper layer was petroleum ether and the lower one was methyl cyanide. White crystals obtained from this latter layer, were identified as acetamide hydrochloride by its m.p., infrared spectrum l2 and mass spectrum.

Spectral measurements For the infrared spectra the Hitachi EPI-G2 spectrophotometer (KBr discs) was used.

Mass spectrum and composition This was determined with the A.E.I. M.S. 902 mass spectrometer.

11 A. Z. Vogel, Practical Organic Chemistry, 3rd ed. p. 174, (1959). 12 E. Spinner, Spectrochim. Acta 15, 95 (1959). 13 Ch. Grundmann, G. Weisse and S. Seide, Ann. Chem. 577, 77 (1952).

The oxidation of methyl cyanide by variadium(1V) chloride 88 (1969) RECUEIL 893

N M R

apparatus.

Gaschromatographic analysis l4

Q 80-100 mesh length 1.8 m; internal diam. l /e inch. Temp. oven: 150".

Results and discussion

following properties :

The NMR spectrum with CC14 as the solvent was obtained with the Varian A60

Gaschromatograph F and M 402. A glass column was used, XE 60 1 % on gaschrom.

The crystalline compound obtained from the oily product, has the

a) M.p. 96". b) According to the mass spectrum the composition of the compound

is C6H3N3C16.

The m/e values and the intensities of the seven peaks of the molecular ion are given in the following Table:

mle

327 329 331 333 335 337 339

Calc. * 50.0

100.0 83.3 37.0 9.3 1.2 0.07

Obs.

50.4

82.6 32.6

100

8.26 1.09 0.09

l4 G. I . Braz, C . V. Myasnikova, A. Ya. Yakubovich, V. P. Bazov and K. I . Sakodynskii, Zh. Obshch. Khim. 33, 6, 1939 (1963).

894 Miss. C. A . A . van Driel and W, L. Groeneveld

Calculated for C6H3N3Ct6 with M = 329.86 21.85

Found 21.94

0.92 12.74 64.50

0.97 12.97 64.34

d) The infrared spectrum was compared with the spectrum, given by Rouschias and Wilkinson 10. Only a few bands were observed at the same wave number (cm-1): viz. 1048 m, 992 m , 828 vs, 770 vs and 746 sh. We found the following additional bands (cm-1) at: 2920 vw, 1570 s, 1552 vs, 1525 vs, 1490 sh, 1435 sh; 1405 s, 1350 m, 1340 s, 1010 sh, 1002 m, 978 m, 852 m, 840 s, 818 sh, 790 vs, 722 sh, 695 vs, 600 m, 580 s , 500 m.

e) The N M R spectrum of this compound consisted of one single band at 3.03 ppm.

f ) The solid compound was also subjected to gaschromatographic analysis (dissolved in CHC13); only one band was obtained. The oil was also dissolved in CHC13 and introduced on to the column. A few small peaks and one large peak appeared, after the same retention time as the solid compound (m.p. 96").

It. was concluded from these observations that the compound, crystallising from the oily product is most probably 2-methyl-4,6-bis(trichloromethy1)- 1 ,3, Striazine, identified by m.p. 1 3 9 l4, chemical analysis, mass spectrum, infrared spectrum l4 and N M R spectroscopy 16.

CH 3

C I

N

C

/ \

I1 I N

C

cc13 / \ / \

C13C N

This compound has been described by many other workers 13*14 because triazines are frequently formed in reactions of R-CN with HCl (except CHsCN, although it can be trimerized to the corresponding s-triazine in the presence of a weak base l 5 .

l5 T. L. Cairns, A . W. Larchar and B. C. McKusick, J. Am. Chem. SOC. 74, 5633 (1952). 16 F. C. Schaefer and J. H . Ross, J. Org. Chem. 29, 1527 (1964).

The oxidation of methyl cyanide by vanadium(1V) chloride 88 (1969) RECUEIL 895

According to many investigations Grundmann el al. l3 stated that, when a mixture of CC13CN and CH3CN is saturated with HCI a “primary product” is formed from two moles of trichloroacetonitrile and one mole of hydrogen chloride :

NH //

ClC3-c I

N \\

I c-c1 cc13

The dienophile addition of C113CN to this diene occurs much more rapidly than the addition of CC13CN and so 2-methyl-4,6-bis(trichloro- methyl)-1 , 3,5-triazine is formed l 3 .

The experiments of Grundmann were repeated by Braz et al. 14. They found not only the formation of 2-methyl-4,6-bis(trichloromethy1)-1,3,5- triazine but also the simultaneous formation of 2,4,6-tris(trichloromethyl)- 1 ,3,5-triazine.

In the experiments described here, only 2-methyl-4,6-bis(trichloro- methyl)-I ,3,5-triazine was obtained. The excess of CH3CN in the reaction mixture is expected to be responsible for the formation of only one product.

In reporting the oxidation of methyl cyanide, the formation of free radicals, such as *CHzCN was suggested, because the formation of hydrogen chloride required the removal of a proton from CH3CN6s7. After the extraction of one proton from the methyl group, the other protons are also removed and CCI3CN is formed. If CI-CHZ-CN and CIZ-CH-CN had been formed, these species would have been detected in the oily product and in the triazines formed.

Thus, we suggest the following procedure for the formation of this triazine:

vcl4 CH3CN + VC13(CH3CN)3 + CI*

CH3CN ____ “’ + CClsCN + 3 HCI several steps

896 Miss. C. A . A. van Driel and co., The oxidation of methyl cyanide, etc.

NH

CH3 I C

2 CClaCN + HCI -+ CIaC-C ____ N // ' N + HCI // CHKN ~

I I C

I C

I \\ / \ / \

N

CCI 3 c-CI C13C N

CCI 3 I

This triazine was found to be the main product in our experiment.

Acknowledgement We wish to thank Dr. J . Reedijk, for his stimulating interest.

(Received .March 14th. 1969).