SwePub - search: WAKA:ref

Enumeration	Reference	Cover	Find
1.	Johansson, Mats H., et al. (author) Alkaline destruction of birch xylan in the light of recent investigations of its structure 1977 In: Svensk papperstidning, Nordisk cellulosa. - 1101-766X. ; 1977-80:16, s. 519-524 Journal article (peer-reviewed)
2.	Johansson, Mats H., et al. (author) Reducing end groups in brich xylan and their alkaline degradation 1977 In: Wood Science and Technology. - 1432-5225 .- 0043-7719. ; 11:4, s. 251-263 Journal article (peer-reviewed)abstract The structure of the reducing end group in xylan can be written: -β-D-Xylp-(1→4)-β-D-Xylp-(1→3)-α-L-Rhap-(1→2)--α-D-GalpA-(1→4)-D-XylIn alkaline media the reducing xylose group is easily isomerized and removed by a β-elimination which leads to a reducing galacturonic acid end group. The 1, 2-linkage between rhamnose and the galacturonic acid explains the retarding effect on the alkaline peeling. Even under fairly mild conditions the galacturonic acid group is converted to other groups which are very stable in alkaline media. Model experiments permit the conclusion that OH-3 in the reducing group is subjected to β-hydroxyelimination. The 3-deoxy-2-O-α-L-rhamnopyranosyl-D-threo-hex-2-enuronic acid group formed is unstable in acid medium and escapes observation by the techniques employed for determination of the end groups.Upon prolonged alkaline treatment and increased proportion of these groups is lost and a rapid peeling proceeds until a xylose group with a 4-O-methylglucuronic acid substituent is liberated. The consecutive reactions of this group are similar to those of the galacturonic acid groups.The formation of 3-deoxyaldonic acid end groups, an important stopping reaction in cellulose, is of minor importance in xylan.The financial support from the 1959 Års Fond för Teknisk och Skoglig Forskning samt Utbildning is gratefully acknowledged.

Johansson, Mats H., et al. (author)
Reducing end groups in brich xylan and their alkaline degradation
1977
In: Wood Science and Technology. - 1432-5225 .- 0043-7719. ; 11:4, s. 251-263
Journal article (peer-reviewed)abstract
- The structure of the reducing end group in xylan can be written: -β-D-Xylp-(1→4)-β-D-Xylp-(1→3)-α-L-Rhap-(1→2)--α-D-GalpA-(1→4)-D-XylIn alkaline media the reducing xylose group is easily isomerized and removed by a β-elimination which leads to a reducing galacturonic acid end group. The 1, 2-linkage between rhamnose and the galacturonic acid explains the retarding effect on the alkaline peeling. Even under fairly mild conditions the galacturonic acid group is converted to other groups which are very stable in alkaline media. Model experiments permit the conclusion that OH-3 in the reducing group is subjected to β-hydroxyelimination. The 3-deoxy-2-O-α-L-rhamnopyranosyl-D-threo-hex-2-enuronic acid group formed is unstable in acid medium and escapes observation by the techniques employed for determination of the end groups.Upon prolonged alkaline treatment and increased proportion of these groups is lost and a rapid peeling proceeds until a xylose group with a 4-O-methylglucuronic acid substituent is liberated. The consecutive reactions of this group are similar to those of the galacturonic acid groups.The formation of 3-deoxyaldonic acid end groups, an important stopping reaction in cellulose, is of minor importance in xylan.The financial support from the 1959 Års Fond för Teknisk och Skoglig Forskning samt Utbildning is gratefully acknowledged.

Träfflista för sökning "WAKA:ref ;lar1:(cth);srt2:(1970-1979);pers:(Johansson Mats H.)"

Refine your search