LessonOne

Le5sonTwo

Less0nThree

LessonFour

LessonFiVe

Less0nSix

LessonSeVen

Less0nEight

LessonNine

LessonTen

LessonEleven

LessonTwelVe

LessonThirteen

LessonFourteen

LessonFifteen

LessonSixteen

LessonSeVenteen

LessonEighteen

LessonNineteen

LessonTwenty

参考译文

总词汇表

附录一 制浆造纸常用术语

附录二 制浆造纸常见缩略语

Lesson One

Text

Molecular Structure of Cellulose

Cellulose was first isolated and recognized as a

distinct chemical substance in the I830s by the noted

French agricultural chemist, Anselme Payen. Payen

concluded, more or less correctly , that cellulose

and starch were isomeric substances because both

had the same carbon and hydrogen analysis and,sub-

jected to hydrolysis, both yielded D-glucose . Yet

the passage of nearly three-quarters of a century

was required before the precise empirical formula of

cellulose was established as (C6H1oO5)x. Results

from earlier studies on acetylation and nitration had

indicated that cellulose had three free hydroxyl

groups per(C6HioO5) unit.

The next major question in unraveling the over-

all structure of cellulose was to determine if cellu-

lose contained only D-glucose units or if it consisted

mainly of D-glucose units with trace amounts of oth-

er sugars. When cellulose was hydrolyzed directly

with acids, over a 90. 7 % yield of D-glucose was ob-

tained. This was good evidence that the only repeat-

ing units in the cellulose polymer were anhydro-D-

glucose. Even better evidence was obtained when

the cellulose was initially converted-into cellulose ac-

etate and then hydrolyzed to a mixture of methyl

glucosides. With this procedure, over 95. 5% yield

of a crystalline mixture of methyl a-and β-D-gluco-

sides was obtained. The reaction is shown below:

The next step in determining the overall struc-

ture of cellulose involved determining how the anhy-

dro-D-glucose units were linked together. To deter-

mine this, samples of cellucose were methylated and

then hydrolyzed to the individual monomeric units.

The position of the methyl groups in the hydrolyzed

units corresponds to the position of the free hydrox-

yl group within the cellulose molecule.