Wood Chemistry
Wood Chemistry
PSE 406/Chem E 470
Lecture 16
Wood Extractives, Components
and Analysis
PSE 406: Lecture 16
1
Wood Extractives II
Wood Chemistry

Agenda
Hydrolyzable Tannins
» Chemistry, biological significance, commercial
uses, pulp and paper problems.

Miscellaneous Extractives
» Tetraterpenes, Phenolics, Alkaloids, Etc.




Extractive Procedures
Extractive Contents
Wood Analysis Procedures
General Wood Compositions
PSE 406: Lecture 16
2
Hydrolyzable Tannins
Structure
Wood Chemistry



Polymers (esters) of a sugar (usually glucose) with one or
more polyphenolic carboxylic acids.
Gallotannins: Gallic acid polymer
Ellagitannins: Ellagic Acid polymer
OH
OH
HO
OH
HO
O C
OH
HO
O
OH
OH
HOOC
OH
COOH
Gallic Acid
Digallic Acid
PSE 406: Lecture 16
O
O
C
C
O
O
OH
OH
Ellagic Acid
3
Hydrolyzable Tannins
Polymer Structure Example
Wood Chemistry
OH
OH
OH
O
Sugar
OH
HO
O
HO
O
O O
O
O
O
OH
O
OH
OH
O
HO
HO
O
HO
OH
OH
OH
O
n
OH
O
PSE 406: Lecture 16
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Hydrolyzable Tannins
Wood Chemistry
General Information

Rare to nonexistent in softwoods.
Hardwoods which contain large amounts:

» Oak (gallic and ellagic tannins)
» Eucalyptus (Ellagitannins)
» Chestnut (gallic tannins)
Hydrolyzable tannins located in heartwood.

Pulp and paper problems:

» Increased consumption of bleaching chemicals.
» Coloration problems.
PSE 406: Lecture 16
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Wood Chemistry


Tetraterpenes
Polymers of isoprene containing 40 carbons (8
isoprene units)
Most common are the carotenoids
» Generally derivatives of lycopene
– This is a carontenoid which is in high concentration in red fruits
(gives color): tomatoes, watermelon, guava, etc.
PSE 406: Lecture 16
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Wood Chemistry



b Carotene
Tetraterpene carotenoid found in dark green and
orange yellow vegetables.
In the human body, it is converted to vitamin A
Has been shown to be have many health related
benefits.
PSE 406: Lecture 16
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Phenolics
Wood Chemistry
CH2 CH CH2

CH2 CH CH2
Aromatic odor
» Balsam odor
» Foliage, bark, fruits
– Sometimes in
heartwood
» Variety of aromatic
compounds
» Typically in small
amounts (1%<)
O
OCH3
O
OH
Eugenol
(Oil of Clove)
Safrole
(75% of Sassafras)
CH2 CH CH2
CH3O
O
O
CH2
Myristicin
(Extracted fron Nutmeg)
PSE 406: Lecture 16
CH2
CH2 CH CH2
CH3O
OCH3
OH
Elemicn
8
Phenolics
Wood Chemistry
COOH
CH
CHO
CHO
CH2 CH CH2
CH
OCH3
OH
OCH3
OCH3
OCH3
Veratraldehyde
(Smells like vanilla)
Vanillin
Cinnamic Acid
(Cinnamon - Bark)
Methyl Chavicol
(Pine turpentine)
CH3
OH
OH
COOH
CH2OH
Salicylic Acid
(asprin - close)
COOH
C O
OCH3
Salicyl Alcohol
OH
Vanillic Acid
PSE 406: Lecture 16
OCH3
OH
Acetovanillone
9
Wood Chemistry
Highly Colored Compounds
O

Anthraquinone
» Found in Teak
» Used as pulping catalyst*

O
Anthraquinone
Naphthaquinones
» Used as UV absorbers
» Used in polymer
products*

O
OH
O
HO
O
Benzoquinones
Lawsone
(Napthaquinone)
O
Juglone
(Pigment in walnuts)
* Produced from other sources
PSE 406: Lecture 16
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Wood Chemistry

Coumarin
Chemical which has the aroma of
fresh mowed hay (or vanilla).
» Produced by white clover.
» When clover is cut, a glycosylated
cinnamic acid is enzymatically
cleaved releasing glucose and a
hydroxy cinnamic acid which
esterifies.


O
O
Coumarin
Coumarin produced in the fruit and
nuts of certain trees (tonka trees for
example)
Coumarin is used as a rat poison.
PSE 406: Lecture 16
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Wood Chemistry
Other Coumarin Facts
HO

Phytoalexins
HO
» Anti-microbial agents


Often exist as glycosides
Can cause health problems
» Coumarin substituted for vanillin by
shady individuals.
» FDA banned coumarin for human
consumption in 1954.

Some coumarins are commercially
used as UV absorbers. (These are
typically synthetic products from
petroleum)
PSE 406: Lecture 16
O
O
Esculetin
CH3O
HO
O
O
Scopoletin
CH3O
HO
O
O
OH
Fraxetin
12
Alkaloids
Wood Chemistry

These nitrogen containing compounds
are found in a variety of different plants.
» Located in the leaves, fruits, and bark.

CH2
HO
H3CO
Quinine
N
» Used to treat malaria
» Isolated from bark of cinchonas (South
American Hardwood)
Quinine
-
OH
– some eucalyptus species
+
N
» Causes pulping problems

N
CH3
Strychnine
» Found in seeds of tree Strychnos nuxvomica (Tropical hardwood)
N
O
O
Strychnine
PSE 406: Lecture 16
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Wood Chemistry

Alkaloids
You are all aware of
the alkaloids shown on
this page you probably
have never seen their
structures. These are
typically found in small
amounts in plants but
are worth large sums
of cash.
O
N
N
O
N
N
N
Caffeine
Nicotine
N
O
O
O
Cocaine
O
PSE 406: Lecture 16
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Miscellaneous
Wood Chemistry

Proteins & Amino acids
» Enzymes used by living organisms are proteins made of
amino acids.
» Plant contain small amounts (~0.5%) of proteins.
» Chlorophyll (need the structure)

Sugars
» Glycosides or free sugars.
– Many extractives in plants have sugars attached which are often
freed in enzymatic processes.
– There are typically low levels of free sugars in plants with some
notable exceptions: sugar cane and sugar beets.

These plants have high levels of free sucrose.
» Some of the water soluble hemicelluloses
– Pectins are often called extractives.
PSE 406: Lecture 16
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Wood Chemistry


Chlorophylls
Probably the most well
known chemicals in plants
are the chlorophylls.
These are tetrapyrroles
that are located in the
chloroplasts of most all
photosynthetic plant
tissues.
As we all know,
chlorophylls give leaves
their green color.
PSE 406: Lecture 16
N
N
Mg
N
MeO2C
N
O
O
O
Chlorophyll a
16
Wood Chemistry

Inorganic Materials
Inorganic materials
» Plants contains small amounts of most metals.
– Some are used by living cells
– Some present as contaminants

Ash content gives a rough idea of the amounts of
metals present.
» Sugar cane: 1.7-3.8% ash
» Corn Cobs: 2% ash

Temperate woods contain 0.1-1% ash while tropical
and subtropical species contain up to 5% ash.
» Main components Ca (50%), potassium and magnesium.
PSE 406: Lecture 16
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Wood Chemistry


Inorganics in Grasses
Grasses contain high levels of inorganics
particularly silica.
Wheat straw: Reported values 4-12+% ash
»
»
»
»
Leaves: 14-19% ash, 10-14% silica
Nodes: 8-14% ash, 5-7% silica
Internodes: 3+% ash, 2+% silica
Potasium: 1%
PSE 406: Lecture 16
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Wood Chemistry
Extraction Procedures
Extraction Technique
Products
Terpenes
Phenols
Hydrocarbons
Lignans
Steam Distillation

Ether Extraction

Alcohol Extraction

Flavonoids
Phlobaphenes
Tannins
Stilbenes
Water Extraction

Carbohydrates
Protein/Alkaloids
Inorganics
Fats/Waxes
Resin Acids
Sterols
PSE 406: Lecture 16
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Wood Chemistry
Western Hemlock
Extractives
% on Wood
Extractive
Wax
0.3%
Flavonoids/Lignans
1.7%
Condensed Tannin
1.7%
Water sol. Carbohydrates
0.8%
Total
4.5%
* Western Hemlock contains only minimal tall oil type compounds
(resin acids, fatty acids, sterols, terpenes, etc)
PSE 406: Lecture 16
20
Non-Volatile Resin Composition
Wood Chemistry
(1960 data for reference)
Spruce
Pine
Aspen
Birch
0.6-1.0%
2.1-9.2%
1-2.7%
1.5-3.5%
- Resin Acids
31%
30-41%
0%
31%
- Free Fatty Acids
0%
3-8%
35%
6%
- Fatty Acid Esters
42%
40-60%
50%
25%
- Unsaponifiables
21%
7-11%
14%
30%
Wood Ether
Extractives
Use this information as a relative comparison only
PSE 406: Lecture 16
21
Wood Chemistry
Extractives in Douglas Fir
Condensed Tannins
Flavonoids
30
25
Stilbenes
Lignans
20
Fatty Acids
15
Resin Acids
Waxes
10
5
0
Sapwood
Heartwood
Information taken from a variety of different sources
PSE 406: Lecture 16
Fats
Neutrals (sterols, etc)
Monoterpenes
22
Wood Chemistry
Quantification of Major Wood
Components
1. Wood Meal Preparation
Wiley
Wood Chips, etc.
Mill
Wood Meal (40-60 mesh)
2. Extraction Using Sohxlet Apparatus (to remove extractives)
a. Alcohol:Benzene (2:1)
b. Acetone
c. Water
3. Lignin
a. Swell with 72% H2SO4 for several hours
b. Reflux in 3% H2SO4
c. Weigh residue = Klason Lignin
d. Hardwood Lignin Soluble Lignin by UV
PSE 406: Lecture 16
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Wood Chemistry
Quantification of Major Wood
Components
4. Holocellulose (Total Polysaccharides)
ClO2
Extractive Free Wood Meal
Holocellulose
Procedure dissolves lignin
5. Alpha Cellulose
17.5% NaOH
Holocellulose
Macerate
Cellulose (Insoluble Fraction)
6. Hemicellulose
Hemicellulose = Holocellulose - Alpha Cellulose
PSE 406: Lecture 16
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Wood Chemistry
Quantification of Major Wood
Components
Wood Meal
Solvent
Extraneous
Soluble in
Neutral Solvents
Extraction
Compounds
Insoluble
H2SO4
Lignin
ClO2
Holocellulose
17.5% NaOH
Insoluble
Cellulose
2N H2SO4
Hemicellulose
(soluble)
D- Glucose
2N H2SO4
Acetyl Groups
Uronic Acids
PSE 406: Lecture 16
Pentoses
Hexoses
25
Chemical Composition of
Wood: Hardwoods
Wood Chemistry
60
50
40
Cellulose*
Hemicellulose*
Lignin*
Extractives
% 30
20
10
0
Red Maple English
Oak
Iroko
Balsa
* Data for Cellulose, Hemicellulose & Lignin on extractive free wood basis
PSE 406: Lecture 16
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Chemical Composition of
Wood: Softwoods
Wood Chemistry
60
50
40
Cellulose*
Hemicellulose*
Lignin*
Extractives
% 30
20
10
0
Douglas Redwood
Fir
Yellow Balsam Fir
Pine
* Data for Cellulose, Hemicellulose & Lignin on extractive free wood basis
PSE 406: Lecture 16
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