Xanthate method

The xanthate method [62] is considered as one of the most promising methods for industrial chemical modification. The principal involved in the xanthate method of grafting is that cellulosic xanthate either ferrated or in acidic conditions reacts with hydrogen peroxide to produce macroradicals. The following reaction mechanism has been proposed ... 

Cotton linters and viscose grade wood pulp were grafted with acrylamide using the xanthate method. The effects of monomer concentration, reaction time, hydrogen peroxide concentration, reaction temperature, and liquor ratio on the grafting process were studied. Optimum conditions for the grafting reaction were established [26]. 

Potassium bisulphate and anhydrous boric or oxalic acid are also used (acrolein from glycerol, pyruvic acid from tartaric acid). Tschugaev s xanthate method belongs to this class of reactions also. 

Kokta, B.V., Lo, R.C. and Daneault, C. (1982). The xanthate method of grafting IX. Grafting of acrylonitrile onto high yield hardwood pulp. In Graft Copolymerization of Lignocellulosic Fibers, Hon, D.N.S. (Ed.). ACS Symposium Series, 187, pp. 269-283. 

Young, R.A. (1977). Modification of high-yield pulps by the xanthate method. Journal of Agricultural and Food Chemistry, 25(4), 738-742. 

The xanthate method has been used in the U.S. and Europe for a number of larger scale pilot plant studies. In the case of rayon, the technique has been explored for flameproofing, high water sorbency, ion exchange characteristics and bacteriostatic and fungistatic properties. Also nonwoven grafted fibers with excellent dispersibility for wet processing and improved binder affinities have been produced. It does not appear, however, that industrial exploitation of these technical successes will take place in the near future. 

It has been shown that the xanthate method could be successfully applied in order to graft hardwood high yield bisulfite pulp made of aspen. The optimum grafting condition, which would give almost 100% grafting efficiency (i.e.,100% formation of true graft and no homopolymer) and rather high monomer conversion of 80% are as follows ... 

The acetyl derivative (30) may be converted by Wolff-Kishner reduction into l,4-dimethyl-3-ethyl-3-piperideine (31).26 The latter compound is obtained in 17% yield also by dehydration of 1,4-dimethyl-3-( l-hydroxyethyl)piperidine (32) by the xanthate method.28 On the other hand, dehydration of the carbinol (32) with phosphorus pentoxide in toluene or by heating in concentrated hydrochloric aoid gives a mixture of isomeric l,4-dimethyl-3-ethylidenepiperidines (33a, b).28... 

Application of other sugars (pentoses and hexoses) as starting materials allowed Jarosz to prepare a number of such useful compounds (such as 83 or 86 in Schemes 36 and 37) using the xanthate method [75,76,77]. 

For the xanthate method see page 654. In the aliphatic series dithiols269 and unsaturated thiols270 are best prepared by Braun s dithiourethane method. 

As with the other syn thermal eliminations, there are no intermediates prone to undergo skeletal rearrangement. The principal application of the xanthate method has been in situations in which acid-catalyzed alcohol dehydration would be accompanied by skeletal rearrangement, or in which a very sensitive olefin is being produced. 

Viscose Generic name for fibers from regenerated cellulose (prepared by the xanthate method) —... 

Viscose vis- k6s [obs. viscose, adj, viscous] (1896) n. (1) A solution of xanthated cellulose in dilute sodium hydroxide from which rayon fibers and cellophane films are formed. The xanthated cellulose is produced by reacting alkali cellulose, i.e., wood fibers or cotton linters treated with sodium hydroxide, with oxygen and carbon disulfide. Rayon produced by this method is known as viscose rayon. (2) Generic name for fibers from regenerated cellulose (prepared by the xanthate method). Tortora PG (ed) (1997) Fairchild s dictionary of textiles. Fairchild Books, New York. 

V. Hornof, B.V. Kokta and J.L. Valade, The Xanthate Method of Grafting of Acrylonitrile onto High-Yield Pulp, J. Appl. Polym. Sci. 20 1543-1554 (1976). 

Cellulose can also be regenerated from solution, the xanthate method being, by far, the most utilized. This regenCTation can be made in the form of wires (rayon) used in textile industry ( 2 million tons) or as films for very divCTse applications. 

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