S D.4 3 3
0 5 .
Published in
Journal of the American Chemical Society
June, 1936

SOME CHARACTI+ ISTICS OF WOOD I
By
ELWIN E . HARRI S
Oa-
In a former publication? it was reported. that maple and spruce lignin isolated by the sulfuric acid method differed with respect t o methoxyl content and reactions with chlorine . The present paper deals with an extension of the former work to determine if the same consistent
' differences exist in lignins from other species of hardwoods and, softllo, ..
Lignins isolated by extraction with methyl alcohol acidified with hydro chloric acid were also included in this study .
The procedure used for the isolation of lignin by the sulfuri c acid method was the same as that recommended in a previous publication i except for the oak which was first extracted with alcohol according to th e modification of Ritter and Barbour= by which some materials not soluble i n alcohol-benzene mixtures or water were remov4d .
The alcohol lignin was prepared by a Mocitiion of the
Friedrich procedure, . in which the material was subjected ,to mild hydrolysi s and fractionation during purification . Brauns and Hibbert= have mor e recently used methyl alcohol with acid as a means of removing lignin fro m wood.
As a further means of comparison, samples of the l,i,gnin b y the two methods were methylated and chlorinated . Moist lignin was methylated by dimethyl sulfate in the presence of sodium hydroxide .
-Presented before the American Chemical Society at its 89th meeting i n
New York City, April 22-26,
1935 0
?E. E. Harris, E . C . Sherrard, and R. L. Mitchell, Journal of the American
Chemical Society, 56, 8 g 9 (1934) .
E. C . Sherrard and E . E. Harris, Ind . Eng. Chem., 24, 103 (1932) .
7, 238-240 (193.5) .
5.A. Friedrich, Z . Physiol . Chem., 176, 14=143
6F. Brauns and H . Hibbert, Journal of the
4720 (1935) .
(192-g) .
.America.
Chemical c1 ety% 55 4
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Lignin, dried in a desiccator, was chlorinated with
i kadwy carbon tetrachloride until it reached the second or light-colored stage .
The chlorolignin showed about 20 percent increase in weight over th e starting proel ct .
Table 1 shows that, with the exee i.marr ,ef 10WOt
off' lignin from oak, a similarity exists among all the hardwood lignins .
Another similarity exists among all the softwood lignins . Except for thi methoxyl content of the fully methylated lignin and the chlorine costoalo of chlorinated lignin, there are distinct differ and softwood lignins as shown especially in the avgdin
Table 2 .
aces t :.6e 01400m(
.
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The li. rins is~olabed by the sulfuric acid . metho ametone,. ab~dia' t 12 percent oit' ►l xdc!ood
of softwood lignin . These soluble fractions had d could be methylated to the same percentage of t same me yl, !a li.
lignins with the same percentages of method arid e 1ori'ne .
ami .k_pmeorib.
corresponding insoluble fraction from which they w e 're se * a
ti a.>em .
ft
The yield of extracted lignin, using methyl alci4 h 'a<n d hydrochloric acid, was low . This may be due to the fact that : y temperature was not high enough . To determine the effect of .Mi.v
solvents on the yield, dioxane and cellosolve were used in ple ' ad alcohol on maple wood . Methyl cellosolve gave a yield of 19 pared of l lignin or 90 percent of the total in the wood . Dioxane gave-a 10 yield or about 50 percent of the lignin . The methoxyl con-6 mt r hi glier in the methyl alcohol and methyl cellosolve lignins . Btauns and Hibberta concluded that this increase was d u e to methylation of one of the- 44pe4y t groups in lignin during isolation . No increase in alkoxyl content wa s found when dioxane was used . These products were easily methylated t o give derivatives with the same percentage of meth l O tMind in methylated sulfuric asir . li .in, indicating that t;_ tie. .l', oai*Iav of possible hydroxyl groups were the same .
;
Methyl alcohol, methyl cellosolve, and & e& is kith ~yflrrechloric acid must also have acted as a demethylating a A t b & se *le lignin left in the wood after treatment contained loss materials when methylated gave a product with 3,2 Ia'erd( sw0k4rLi
Demethylation has been observed by other investLgatorsi but much more drastic and without simultaneous methylation .
Wove undser conditOMP
During chlorination both hardwood and softwood . lignins los t methoxyl . Sulfuric acid lignin from hardwoods lost about one-third of it s methoxyl and from softwoods about two-fifths . Methyl alcohol lignins from
-'
1
A
1E . Heuser and R . Schmitt, Cellulosechemie, 1, 49_58 (1920) ; 2, 81 (1921) .
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Table 1 .--Characteristics of wood lianin s
Wood
Sugar maple
Sugar maple
Sugar maple**
Aspen
Aspen
Aspen**
'
MeO : MeO .
.
Method : Yield* :content :content
of
: isolation: lignin :isolated:
:
: of : of
:
.
.
:methylated:
MeO : Cl
Hardwoods
:70% H2SO4 : 21 .0
: 20 .7
: 32 .0
:MeOH-HC1 : 6 .0
: 25 .3
: 32 .2
:70% H2SO4 : -1 7 . 3
11 .8
: 27 . 0
15 .0
: 26 . 0
-x. :70% H2SO4 : 20 .4
20 .4
31 .9
: Me0H- IC1 : 7 .0
: 25.6. .
: 32 .0
:70% H2604 : -: 17 .3
12 .0
25 . 7
14 .6
: 25 .1
White oak
White oak
Beech
Beech. . :
Beech**
Basswood
Basswood
Basswood**
:70% H2 S04 : 25 . g ' :
: Me OH-HC 1 : 7 .0
:
20 . 5 - :
25 .4
:
3117
31 .9
:
:
11 .7
14.5
.
:70% H2SO4 : 22 .5
.
20.6
: 31.9
:MeOH-HCl
:70% H004- :
6 .0 . : 25 .5
: 32 .0
-.
17 .3
: --
25 .6
25.. 6
11.7
.
26 .0
14. g 27 .0
:70% H2SO4 ; 19 .0
HC1 : 6 .0
:
:
20.5
25 .5
70% H2.S04 : -: 17 .3
32 .0
: 11 . g : 25 .0
14 .9
26 .6
Spruce
Spruce
Spruce**
Softwoods
70% H2SO4 ; 26 .9
: 17 .0
:
:M
:70% H2204 : -14.5
:
3.2 .0
l : 4.0
: 21 .5
: 32 .0
g.8
26 . g
12 .1
: 26 .3
8 .5
2.5:3
-11 .7
: 2W
Slash pine
Slash pine
Slash pine**
:70% M004 : 25 .5
: 16 .9
: 31 ..9
:MeOH-HC.1: 4 .0
: 21 .6
: 32 .0
:70% H2SO4 : 14 .5
:
Eastern. hemlock. . :70% H2 SO4 30.06 :
16 .9
: :
Eastern hemlock. . :MeOH-HC1 : 4.0
: 21.6
Eastern hemlock** :70% H2SO4 : -: 14.5' :
.
32 .0
:
:
-g :.7
215:,4 .
n .6
: 27-• - ' '
*Yield calculated from the dried extracted woof .
**Sample was that remaining after extracting four times
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Table 2 .--Average composition of wood lignin and lignin derivative s
'- 5
+ L .
Material analyzed
Found :
: Calculated : number of : Found :
: group :
Calculated * number o f group
:Percent : : Percent:
MeO in lignin from residue after : extraction with McOH-HC1 : 17 .3
MeO in lignin from wood by
70% H2 SO4
:
: 20.5
:
5.02*
6 .04* :
: 14.5 :
16 .9 :
4.14*
4.91*
MeO in lignin from wood by
MeOH-HC1 : 25 .5
:
MeO in fully methylated lignin . . . : 32 .0
:
Chlorinated H2 S04 lignin (Me0
: 11.8
: 25 .7
:
7 .63*
10 .0
4.18**
7 .98
:
21 .6 : 6 .42*
32 .0 : 10.0
8 .7
: 3 .05* *
: 25 .5 : 7 .85
Chlorinated MeOH-HC1 lignin (MeO : 14.8
:
(Cl : 26 .2
:
5 .25** : 11.8 : 4 .1g* * g .l
: 26 .7 : 8 .15
*Calculated on the basis of 10 methoxyl groups in fully methylated lignin .
**Calculated on the basis of 1100 for the molecular weight of the chlorolignin with four methoxyl groups .
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hardwoods lost about two-sevemthid of their r it e. aad about one-third . On the basis of 10 methoxyls in t4llly K this loss .in each case is. _ AVAWA4 rl : during chlorination was about the-dome as the the chlorolignin . It seems therefore that chlorine reacted by addition o r substitution rather than by oxidation .
w
.actin
= m softwoods
, tee.
f ced ice.
1 g*o
-TnC gg2 d'n Wet tt -al' .
In a former publication? the fully methylated compoun d containing 32 percent methoxyl was assigned 10 methoxyl groups . Table 2 shows the values for the numbers of methoxyl groups in the isolated ligni n and lignin derivatives calculated on the basis of 10 methoxyl groups i n the fully methylated derivatives . The values for the methoxyl groups ar e close to whole numbers except for the lignins isolated by the action o f methyl alcohol and hydrochloric acid . These values are intermediat e between two whole numbers and therefore the products must have been mixture s of lignin derivatives with different numbers of methoxyl groups .! The Ilmono methylated" product described by Brauns and I1ibber tb must also have been a mixture . Hardwood lignin as it occurs in wood contains six methoxyl group s and when fully methylated contains 10 methoxyls . Softwood lignin contains five methoxyls and is methylated to a compound containing 10 . When the lignin is isolated by extraction with methyl alcohol and hyd r.
Qe loric acrid some of the hydroxyl groups are methylated . At least one of the methoxyl s introduced in this manner is resistant to the action of chlorine . There at e two methoxyl groups in the sulfuric acid lignin and two in the methy l alcohol lignin from both hardwoods and softwoods which are removed by th e action of dry chlorine .
Conclusions
The previously reported differences between maple and sp e lignins by the sulfuric acid method have been found to exist between th e lignin from other hardvio:ods and softwoods ; four other hardwoods being ve_ y similar to maple and two .othov •softwoods very similar to spruce .
On the basis of 10 methoxyl groups in the fully methylated lignin , hardwood lignins isolated by the sulfuric acid method contain six and softwood five methoxyl groups .
About 30 percent of the lignin in hardwoods and 15 percent,i n softwoods is removed by the action of methyl alcohol-hydrochloric acid .
With both hardwoods and softwoods the part removed is methylated by abou t one and one-half groups and the insoluble residue is demethylated by abou t one group . All these fractions from both hardwoods and softwoods by eithe r the methyl alcohol-hydrochloric acid or sulfuric acid method of isolatio n can be methylated by dimethyl sulfate to 10 methoxyl groups .
Lignins from hardwoods or softwoods by either the sulfuric aci d or alcohol methods lost two methoxyl groups when treated with dry chlorine .
Recent work at this Laboratory has shown definitely that these product s are mixtures .
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