东北林业大学2005－2006学年第一学期考试试题考试科目：木材化学.DOC

考试科目： 木材化学 考试时间：120分钟 试卷总分60分 题号 一 二 三 四 五 卷面成绩 平时成绩 总分 得分 评卷教师 得分 一、Fill in the blanks:（每空1分，总计15分，要求用英文答题，如用中文则分数减半，答案填在空格内） The main chemical constituents are cellulose, hemicelluloses, lignin, and extractives. According the figure, A is the warty layer, B is the inner layer (S3), C is the middle layer (S2), D is the outer layer (S1) of the secondary wall, E is the primary wall (P), and F is the middle lamella (ML). In 1897, Peter Klason studied the composition of lignosulfonates and put forward the idea that lignin was chemically related to coniferyl alcohol. Lignins are polymers of phenylpropane units. One of their main coupling modes is β-O-4 . Besides cellulolytic enzyme lignin, the so-called Bj?rkman lignin, alternatively referred to as milled wood lignin (MWL) is the best preparation known so far, and it has been widely used for structural studies. During kraft pulping, the presence of hydrogen sulfide (HS-) ions greatly facilitates delignification because of their strong nucleophilicity in comparison with hydroxyl(OH-) ions. The hemicelluloses are peeled much more readily than cellulose. The prerequisite for the peeling reaction is the presence of a reducing end group (a hemiacetal group) in the polysaccharide chain. 得分 二、True or False:（对的打√，错的打×，答案填在题后的括号内。本大题共10小题，每小题1分，总计10分） During Kraft pulping roughly half of the wood substance degrades and dissolves. The organic matter in the black liquor is composed of the degradation products of lignin and polysaccharides in addition to a minor fraction comprising extractives. (√) The lignin present in hardwoods is partly dissolved during the acid hydrolysis and hence the gravimetric values must be corrected for the "acid-soluble lignin" using UV spectrophotometry. (√) (-Aryl ether linkages in free phenolic structures are cleaved relatively easily during the initial phase of delignification. (√) (-Aryl ether linkages in nonphenolic structures are cleaved much more slowly,