David Wang’s Wood Chemistry Class -...

Extractives

David Wang’s Wood Chemistry Class

• 抽出成分(extractives)係指存在於木材細胞腔、細胞壁或中膠層中，因樹木生理代謝或受外力刺激影響

所產生之成分。

• 它可以經由水蒸氣蒸餾或中性溶劑萃取出來。通常，抽出成分之含量雖僅佔木材重量之5-10 %，但是它的存在卻賦予木材吸引人的外觀及多樣化的性

質，包括: 顏色、耐久性、加工性質……等，故又將其稱為木材特殊成分。

•木材是由主成分和副成分所組成，如果是以此角度來看，「木材抽出成分」應要歸於這裡所指的副成分。而又如以樹木的生理代謝角度來看，抽出成分應是要歸屬於植物的二次代謝產物(secondary metabolites)。

•Distribution

•Amounts

•Variations

Extractives

Extractives are the wood constituents which can be

extracted with neutral solvents.

Extractives are obtained by extraction wood with

organic solvents or water or steam distillation, and

some are obtained as exudates from wounded

trees.

The amounts of extractives is small, generally up

to 5-10% in the wood in the temperate zone.

However, in some tropical woods relatively high

amounts of extractives are found.

Extractives Among wood species, differences of major components of

wood are few. However, a great diversity in extractives are found through wood species.

Although the extractives are low in concentration compared with those of the cell wall polymers, this fraction characterizes each wood species chemically.

Most component of wood extractives are classified as secondary metabolites, and the distribution of specific compounds in certain wood species. This feature provide the basis of chemotaxonomy of woody plants.

Extractives

Individual compounds are often found in specific

tissues of individual trees, and their amounts can

vary from season even in the same tissue.

Extractives are the predominant contributors to

wood color, fragrance, and durability. Extractives

also influence the pulping, drying, adhesion,

hydroscopicity, and acoustic properties of wood.

Many extractives have specific biological activities,

and various woods have been used as source of

crude drugs and medicines for centuries.

Extractives Exudates

Exudates are formed by the tree through secondary metabolism after mechanical damage or attack by insect or fungi.

Resin Resin is often used as a collective name for the lipophilic extractives

soluble in nonpolar organic solvents but insloluble in water. Different types of extractives are necessary to maintain the diversified

biological functions of the tree. Fats: the energy source of the wood cells. Lower terpenoids, resin acids, phenolic substances: protection the

wood against microbiological damage or insect attacts. Metal ions: catalyst of enzyme for biosynthesis.

Phenolic compounds

Terpenoids

Alkaloids

Others

Classification of Natural Products

Terpenoids and Steroids

Occurrence The softwood resin canals are filled with oleoresin.

Oleoresin: monoterpenoids and especially resin acids (diterpenoids) are dominant and commercially important oleoresin constituent.

The parenchyma resin of both softwoods and hardwoods contains triterpenoids and steroids, main occurring as fatty acid esters.

Some tree produce rubber, gutta percha, and balata, which polyterpenes.

Classification and Biosynthesis of Terpenoids

Terpenoids and steroids are formally derived from isoprene units and are sometimes called isoprenoids.

The name terpene was given to hydrocarbons which were detected in terpentine oil.

Terpenes are known as the large group of hydrocarbons made up of isoprene units (C5H8). Their respective derivatives with hydroxyl, carbonyl, and carboxyl functions are not hydrocarbons but strictly speaking terpenoids. → It has been proposed to call both the terpene hydrocarbons and their derivatives collectively terpenoids.


Steroids are structurally related to terpenoids, but

some pathways in their biosynthesis have resulted

in their structural characteristics and biological

function.

Terpenoids can be divided into subgroups according

to the number of isoprene units.

Classification of Terpenes (Terpenoids)


Isoprene itself had been characterized as a decomposition product from various natural cyclic hydrocarbons, and was suggested as the fundamental building block for isoprenoids.

Isoprene is produced naturally but is not involved in the formation of these compounds (terpenoids), and the biochemically active isoprene units were identified as the DMAPP (dimethylallyl diphosphate) and IPP (isopentenyl diphosphate).

Classification and Biosynthesis of

Terpenoids

Relative few of natural terpenoids conform exactly to the simply concept of a linear head-to-tail combination of isoprene units as seen with geraniol, farnesol, geranylgeraniol.

Squalene and phytoene display a tail-to-tail linkage at the centre of the molecules.

Most terpenoids are modified further by cyclization reactions, but the head-to-tail arrangement of the units can usually still be recognized such as menthol, bisabolene, and taxadiene.

Head-to-tail coupling mechanism of terpenoids and steroids

geranyl pyrophosphateIsopentenyl diphosphate

farnesyl diphosphate

Biosynthesis of Terpenoids and Steroids

Biosynthesis of Terpenoids

The prenylation reaction is stereospecific, mediated

by a type of prenyl transferase enzyme, which

generates mainly isoprenoids with trans

configuration.

In contrast, rubber has an all-cis configuration

because its synthesis is controlled by another type

of prenyl transferase enzyme.

Extremely simplified reaction scheme illustrating potential products arising from the oxidation of isoprene by the OH radical

Factors driving BVOC emissions and biological and physico-chemical processes affected by these emissions. Many internal (genetic and biochemical) and external (abiotic, such as temperature, light, water availability, wind and ozone, and biotic, such as animal, plant and microorganisms interactions) factors control emission rates of different BVOCs by altering their synthesis, vapor pressure or diffusion to the atmosphere. The complex net of these factors, their interactions and the different responses of the different BVOCs produce large qualitative and quantitative, spatial and temporal variability of emissions and frequent deviations from current standard emission models, mostly based on temperature and light response. Plant emissions of BVOCs have strong relevance for plant physiology and plant ecology, atmospheric chemistry and climate.

Biogenic volatile organic compounds might confer thermotolerance to plants

Monoterpenoids

Monoterpenoids are dominant in the volatile terpenoids fraction (essential oil) as turpentine from different parts of the tree by steam distillation or from the digester relief condensates after softwood KP.

Monoterpenoids can be divided into acylic, mono cyclic, bicyclic, and tricyclic structural types.

Monoterpenoids are derived from geranyl pyrophosphate (GPP)

Tropolones, a seven-membered ring compounds, are belong to monoterpenes.

Monoterpenoids

單萜類化合物廣泛存在於高等植物的分泌組織中

唇形科 (薄荷、紫草、霍香)傘形科 (茴香、當歸、芫荽、白芷、川芎)菊科 (艾草、茵陳蒿、木香)芸香科 (橙、菊、花椒)樟科 (樟樹、肉桂)

單萜類多數是植物揮發油(volatile oil，又稱為精油 essential oil)中，低沸點(140-180 ℃)成分的主要組成。這些成分的含氧衍生物具較高的沸點(200-230 ℃) ，且大都具有濃郁的香味，在醫療工業、香料工業、昆蟲訊息素及昆蟲忌避劑等方面具廣泛的應用。

揮發油的特性

大都無色或淡黃色、具特殊氣味，一般在室溫下可揮發。

比重一般比水(0.85-1.18)輕，僅少數比水重 (如丁香油、桂皮

油) 。

難溶於水，可完全溶解於無水酒精、乙醚、氯仿、脂肪油中。

具一定的旋光性與折射率，為鑑定質量的重要依據，一般揮發油的折

射率在1.45-1.56之間。

無確定的沸點與凝固點。

在低溫時，揮發油常可有固體物質析出。

單萜化合物的萃取

蒸餾法

水蒸餾法

水蒸氣蒸餾法

溶劑萃取法

壓榨法 (冷壓法)

脂肪萃取法

超臨界萃取法

Common Monoterpenoids Present in Essential

Oils and in Commercial Turpentines

myrcene

α-pinene β-pinene

limonene

camphene3-carenehinokitiolborneol

R = H

β-phellandrene

Monoterpenoids Uses

Turpentine (solvent)

Fragrance and flavor chemicals

Polyterpene resins

Insecticides

Pine oil

Sesquiterpenoids

More than 10000 sesquiterpenoids have been identified, representing a wide variety compounds of different skeletal types from acyclic to tetra cyclic systems.

α-muurolene δ-cadinene α-cadinolα-cedrene

logifloene juniperol nootkatin chanootin

Diterpenoids

Diterpenoids constitute a major

part of oleoresin.

This group can be divided into

acylic, bicyclic, tricyclic, tetracyclic,

and macrocyclic structural types.

Diterpenoids are present either as

hydrocarbons or as derivatives

with hydroxyl, carbonyl, or

carboxyl groups.

geranyl-linalool β-epimanool

cis-abienol manoyloxide

pimaral

pimarolcembrene

Diterpenoids

The resin acids are dominant constituents in pine wood oleoresin and in commercially important rosin. The most common resin acids in softwood are tricyclic terpenoids,

and they are classified into pimarane and abietane types.

Pimarane type

Abietane type

Diterpenoids

The resin acids of the abietane type with conjugated

dienoic structure are less stable against isomerization and

oxidation than those of pimarane type.

Due to hydrophobic skeleton in combination with a

hydrophilic carboxyl group, the resin acid soaps are good

solubilizing agents, and together with the fatty acid soaps

they contribute effectively to the removal of neutral

lipophilic substances from wood in KP pulping and

subsequent washing.

Diterpenoids

Besides the common resin acids, some bicyclic resin acids are known.

Labdane type resin acids are present in some pines. Secodehydroabietic acid, also found from levopimeric acid

KP.

Communic acid

mercusic acidsecodehydroabietic acid

lambertianic acid

Triterpenoids and steroids

sitosterol campesterol sitostanol

citrostadienol

betulin serratenediol


Compounds belonging to this group are widely distributed in plants.

The most common steroid in wood and higher plants is sitosterol.

Campesterol is a structurally similar monoenoic steroid but is less abundant than sitosterol.

Citrostadienol is a dienolic sterol having a 4α-methyl group.

Betulinol (betulin) is a pentacyclic triterpenoid occuring in large amounts in free from in the outer bark of birch. Serratenediol present in the bark of pines, is a member of a small pentacyclic triterpenoid subgroup so-called serratanes, having a seven-membered C-ring.


Triterpenoids and steroids occur mainly as wax and

as glycosides, but also in the free form.

Hydrophobic compounds – causing problems in

pulping and papermaking process.

Sitosterol and betulinol are potential raw materials

for making wood chemicals.

Polyterpenoids

Acyclic primary alcohols of polyisoprenoids, so-called polyprenols, are abundant in high plants, especially in the

leaves, but in wood.

A special type of polyprenols, called betulaprenols, occur as fatty acid esters in silver birch. Betulaprenols are built up

6-9 isoprene units, which double bonds have cis and trans configuration.

Polyterpenoids

Rubber, gutta percha, and balata

The degree of polymerization is

high in these natural products.

Different sterochemistry

Natural rubber: all cis configuration

Gutta percha and balata: all trans

configuration.

Fats and Wax

Fats and wax are the predominating constituents of the lipophilic material encapsulated in parenchyma cells.

The fats are glycerol esters of fatty acids occurring in wood predominantly as triglycerides.

In fresh wood free fatty acids are present practically only in heartwood.

Fatty acids are partially liberated from triglycerides during wood storage.

More than 30 fatty acids, both saturated and unsaturated, have been identified in softwoods and hardwoods.

• Among the unsaturated C18-fatty acids, oleic acid (monoenoic) and linoleic acid (dienoic) are the predominating components.

• Linolenic acids (trienoic) is a common, although a minor component in both softwood and hardwoods. Pinolenic acids is linoenic acid's isomers, it is a major fatty acid in pines and spruce.

Fats and Wax

Waxes are esters of higher fatty alcohols (C18-C24),

terpene alcohols, or sterols.

Fats and waxes (esters) are hydrolyzed during kraft pulping. The fatty acids, which are liberated, can be recovered together with resin acids as soap skimming from the black liquor.

Phenolic Constituents

Heartwood and bark

contain a large variety of

complex aromatic

extractives. Most of them

are phenolic compounds,

and many are derived from

the phenylpropanoid

structure.

Classification of Phenolic Compounds

Phenolic Compounds

Summery of the Biogenetic Connection between a Selection of Familiar Phenolic metabolites



LignansIsolation Procedures

• Lignans can be isolated from the bark, fruit, heartwood, leaves, roots and resin of plants

• Most isolation procedures involve solvent extraction, chromatography separations, and crystallization

• Lignan yields can vary from 0-30%

LignansCommercialization

• Large amount of research devoted to investigating medicinal properties of lignans– Particularly from tropical hardwoods and grasses

• Example 1999 reference: 35 lignans isolated from the twigs of Tazus mairei

– Antiviral– Antitumor– Biocidal– Bioactive Agents

Color Compounds Isolated from Taiwania Heartwood

Taiwanin A Savinin Helioxanthin Pluviatolide

Taiwanin I Ferruginol T-Cadinol Secoabietane dialdehyde

Flavonoids/TanninsIsolation of Flavonoids

Isolation of flavonoids accomplished through solvent extraction

Hot water

Alcohols

Solvent fractionation of extract

Salting out

Crystallization

Flavonoids/TanninsIsolation of Flavonoids

Flavonoids concentrated in certain parts of plants

Plant sourcesPulp of fruitsBroccoli, green peppers, onions, etc.Green tea, red wineHerbsTree bark

Flavonoids/TanninsPolymerization Reactions

• Condensed tannins are formed through the polymerization of flavan-3-ol (catechin) and flavan–3,4-diols (leucoanthocyanidins)– In tree, polymerization through

acidic enzymatic non-oxidative coupling

– 2-50 units • Typically 2-8

– Linkages can be through a variety of sites

Condensed TanninsProperties

• The term condensed tannins refers to a mixture of polyflavonoids of different MW (500-5000) characterized by different linkages, functional groups, and stereochemistry.

• Protein binding capacity: tannins will bind with proteins causing them to precipitate.– This was the definition of tannins: compound which will

precipitate proteins.

Condensed TanninsSources

• Condensed tannins more prevalent in

hardwoods but present in softwoods

–Wattle (Acacia - Southern Africa)

–Quebracho (Schnopsis - South America)

–Mangrove (Rhizophora -)

–Hemlock (North America)

Condensed TanninsBiological Significance – Insects/Animals

• Protection of plants against insects/animals–Some evidence for/some against

• Bad Taste/Astringency (bitter taste)• Appears to be major factor• Particularly bad for insects not used to tannins

• Animals: tannins reduce digestion of food–Interaction with digestion enzymes

• Toxic to bacteria

Condensed TanninsBiological Significance - Fungus

• Pine calluses: created by fungal invasion– Tree forms calluses as protective tissue– Calluses contain high levels of tannins (Chinese 50-80%)– Concentrations of tannins as low as 0.1% or 0.8 % have

been shown to retard the growth of a large number of parasitic fungi

• Quote: Edwin Haslam (tannin chemist)– “serious and nagging fear that a part at least of (their)

scientific career(s) has been spent inspecting the loot in the garbage bin of plant metabolism”

Hydrolyzable TanninsStructure

• Polymers of a sugar (usually glucose) with one or more polyphenolic carboxylic acids: linked through ester linkages

• Gallotannins: Gallic acid polymer• Ellagitannins: Ellagic Acid polymer

Hydrolysable TanninsPolymer Structure Example

Sugar

Hydrolyzable TanninsTree Information

• Rare to nonexistent in softwoods

• Hardwoods which contain large amounts:

– Oak (gallic and ellagic tannins)

– Eucalyptus (Ellagitannins)

– Chestnut (gallic tannins)

– Myrobalan fruits (cherry plum)

• Hydrolyzable tannins located in heartwood

Condensed TanninsUses

• Leather tanning: 10,000+ year old industry–Vegetable tannins & chrome –Tannins interacting with proteins in hides

• Adhesives–In phenol formaldehyde systems, tannins speed up the

set:

• Oil well drilling fluids: old but effective use: taken over by chrome lignosulfonates

Stilbene 二苯乙烯類之化合物是以α，β-Diphenyl ethylene 為骨架之化合物稱之，廣泛地分佈在針葉樹皮及闊葉樹之許多樹種。由於具有共軛

雙鍵，此類化合物為反應性極強之化合物，除

了在製漿蒸煮過程中會與藥劑反應外，並會阻

止可溶性之木質素磺酸鹽的形成，阻礙木質素

的溶解。此外，二苯乙烯類亦與木材之抗蟻性

有密切的關係。

Inorganic Components

Wood contains only rather low amounts of inorganic components, measured as ash seldom exceeding 1% the dry wood weight. Ash content of needles, leaves, and bark can be much higher.

Typical deposits in the cell walls are various meta salts, such as carbonates, silicates, oxalates, and phosphates. The most abundant metal component is calcium followed by

potassium and magnesium. A spectrum of other metals is also present, amounting up to 100

ppm for iron and magnese whereas most of the other metals usually occur only as traces or at least below the 10 limit ppm.

Contribution of Extractives to Wood Characteristics Color in Wood

Chemical structure and color Color of wood Pigments occurring in wood

Odor in Wood Volatile components Fragrant components Foul-smelling components Removal of foul odors Insect attractants

Physical Properties Wood density and strength

Role of wood exudates and extractives in protecting wood from decay Effect of extractives on pulping

Pulping processes Chemical Increased consumption of pulping liquors Effect on pulping processes Effect on equipment during pulping Pulp properties

Color changes arising during pulping and bleaching Speck formation and pitch problems during pulping and bleaching

Spent liquor recovery Observations

Inhibition of resin and glue curing by extractives Inhibition of cement hardening by extractives Color change

Color changes upon exposure to light Color changes by other agents

Water soluble compound Blue-black stains Blue stain

Effect of Extractives on the Utilization of Wood

Color in Wood – Chemical structure and color

Of the solar radiation hitting the earth, that with wavelength between

approximately 380 and 750 nm penetrates the atmosphere most

readily.

The human eye is not sensitive to all wavelengths, but is limited to a

wavelength sensitivity from around 400 to 700 nm.

Substances that have the special property of absorbing all or a part

of visible light are the coloring matter or pigments.

Chromophores and Auxophores.

Chromophores and Auxophores

Color in Wood –Color of wood

Color is one of the most distinctive properties of wood, and is of considerable importance in woods that used for decorative purposes.

Color does not depend upon the main structural components, but rather upon the minor components.

The coloring matter and other constituents of dead tissues such as heartwood and outer bark are difficult to isolate and characterize because, as this tissue die, the enzymatic functions in the cell become disordered, and cell contents undergo oxidation and polymerization.

Color in Wood –Color of wood

Although colored extracts may be separated from most woods by extraction with suitably neutral solvents, it is generally impossible to remove all the coloring mater in this way.

The chemistry of coloring matters of wood is frequently very complex, and few of them have been investigated or elucidated in detail.

The colored extractives isolated from heartwoods have been investigated since about a century ago and have been shown to posses special constitutions related to phenolic and quinonoid structures.

Coloring Constituents isolated from Wood

Taiwanin A (Taiwania cryptomerioides)Red orange

Sulfuretin(Rhus cotinus)Orange yellow

4-hydroxydalbergione-4’-methoxy-dalbergione(Dabergia spp.)Orange

Tectoquinone(Tectona grandis)

Mansonone F(Mansonia altissima)Purple

Mamegaki-quinoneEbony (Diospyros spp.)

Order in Wood – Volatile components

An order is detected by the olfactory organs when the

molecules of volatile substances reach the olfactory cells

and stimulate them.

Wood odors can be classified into two groups according to

the formation process of the odor source.

Order is produced during normal three metabolism

Order is formed as by-product of decomposition of some wood

components by parasitic microorganisms.

Order in Wood – Volatile components

The odor compounds in wood are usually in a liquid state at room temperature. They can classified by chemical structure Mono- or sesquiterpenes (e.g. α-pinene, camphor, cedrene)

Aromatic compounds (e.g. methyl salicylate, safrol)

Nitrogenous compounds (e.g. pyridine, 3-methylpyrrolidine)

Sulfur compounds (e.g. allylsulfide)

The latter two groups are rarely formed except as bad-smelling components.

Order in Wood – Fragrant components

Fresh wood after cutting has a characteristic odor that that diminishes continuously over time. Some species retain a fragrance for a long time, which gives them additional value.

The odor of wood can sometimes be used for the identification of wood species.

The essential oils of tree are presumed that they protect the tree and preserve it from decay, repel, act as a waterproofing, etc.

Some of these fragrant components emitted from the leaves into atmosphere act as phytocides, the so-called “green showers” that are coming into popular concern.

Some tropical woods, such as sandalwood (Santalum spp.), and styrax (Liquidambar spp.), have been used as incense woods since ancient time.

Main Odor Constituents of Some Conifer Woods

Cryptomeria joponica

δ-cadinene δ-cadinol copaene β-eudesmol

Chamaecyparis spp.

bornyl acetate campheneα-terpineol

α-pinene β-pinene

myrcene

Main Odor Constituents of Some Conifer Woods

Cunninghamia spp.

cedrol caryophyllene α-cedrene

Taiwania cryptomerioides

α-cadinol T-cadinol T-muurolol δ-cadinol

Main Odor Constituents of Some Deciduous Woods

Cinnamomum spp.

camphene camphor1,4-cineol

1,8-cineol

cinnamaldehydeeugenol linalool safrol

Main Odor Constituents of Some Deciduous Woods

Santalum album

X = CH3, α-santalene

X = CH2OH, α-santalolX = CH3, β-santalene

X = CH2OH, β-santalol

Order in Wood –

Foul-Smelling components

Several species with foul orders cause problems in

wood industries, such as lumber sawing and the

manufacture of plywood and laminated wood.

Elima wood (Octomeles sumatrana): pyridine and 3-

methylpyrrolidine.

Bawang hutan (Scordocarpus borneensis): sulfides.

Odor problems are almost always caused by woods

colonized by microorganisms.

Order in Wood – Foul-Smelling components

The bad odor is usually formed during wood storage in the log pond by fermentation of available carbohydrates.

These foul-smelling substances, which vary among wood species but generally have an odor of fermenting compost or feces, have been determined by GC to be mainly C4 and C5 fatty acids (butyric and valeric acids).

The foul odor of ramin results from metabolic products of microorganisms growing on carbohydrates and proteins in the wood.

The Odorous Components of Ramin

n-butyric acid isovaleric acid

caproic acid caprilic acid

skatole

Physical Properties

Contribution of Extractives to Wood Physical Properties

The effect of extractives on physical properties of wood

have not been clarified because this question involves

chemistry, physics, and structural dynamics.

It is well know empirically that wood species containing

large amounts of extractives have better durability,

dimensional stability, and plasticization; for these reasons,

extractives-rich woods have been used for construction

and fancy goods since ancient times.


Inhibition of resin and Glue Curing by extractives Resins are an essential component of many paints and glues. When

wood is painted or glued, extractives sometimes inhibit resin curing.

The inhibition often occurs when unsaturated ester are used in the resin.

Many wood species are known to contain inhibitory extractives. Phenolic compounds and benzoquinones are common substances shown to

be inhibitory to polymerization of vinyl monomers.

Wood rich in n-hexane extractives is inclined to inhibit polymerization. Ether-soluble extractives can entry paint resin and inhibit curing.

Extractives Detrimental to Paintability

Ferruginol (Cryptomerioides japonica)

Vallinic acid(Dryobalanops spp.)

Taxifolin(Larix leptolepis)

Taiwanin E(Taiwania cryptomerioides)

Mansonone-G methyl ester(Zelkova serrata)

Role of wood exudates and extractives in protecting wood from decay

The vast of wood-rot fungi belong to the class Basidiomycetes.

Toxic extractable substances deposited during the formation of heartwood are the principal source of decay resistance of heartwood. Antifungal compounds of polyphenol from the

heartwood. (1)Hydroxymatairesinol, (2) Pinosylvin, (3) Oxyresveratrol, (4)Dihydromorin.

Chemical structure of Angolensin of ether extractives of Pterocarpus indicus

Antifungal compounds of tannins from the heartwood. (1) Gallic acid, (2)Ellagic acid

Volatile components of the methanol extractives of Hinoki heartwood (1)α-Cadinol, (2)T-Muurolol, (3)T-Cadinol, (4)γ-Cadinene.

Configuration of 5 compounds isolated from the hexane fraction of Taiwania heartwood. (1)Taiwanin A, (2)α-Cadinol, (3)α-Cedrol, (4)Hinokiol, (5)Sugiol.


Inhibition of cement hardening by extractives There are many case in which wood is used in contact with

concrete, such as cements mixed in or molded with wooden forms, or cement and wood are mixed together for board production.

Cement yield calcium ions when mixed with water and exhibits a pH = 13. The alkaline solution dissolves extractives from wood into the slurry. The resulting substances have a low solubility and they precipitate with CaO. CaO is one of the most important chemical compounds in concrete, and its loss retards the normal hydration reaction.

Many substances are known to be inhibitory to cement hardening

Sucrose, galactose, fructose, glucose, lactose, dextrin, glycogen, mannitol,

tannic acid, succinic acid.

Most of above compounds are sugar and common wood extractives .

Sucrose may be one on the most effective.

The sugars and tannin on the inhibition of cement setting can be

ascertained. Hot-water extracts from wood meal are developed on

thin layer chromatography and then sprayed with a cement slurry

instead of chemical reagents to detect inhibitory substances.

Effect of Extractives on Pulping

Increased consumption of pulping liquors

The alkali in alkaline pulping processes is consumed by reaction

with lignins, by degradation of the carbohydrates, and by reaction

with organic acids and the extractives presents in wood.

Acidic and polyphenolic extractives react rapidly with NaOH so that

the mount of alkali available for deligification is reduced.

resveratrol


Effect of equipment during pulping

The volatility of acids and particularly of tropolones results in corrosion

of the dome of digesters and upper parts of pulping equipment.

The vicinal trihydroy phenolic moieties in elligitannins and

proanthocynidings of eucalypts rapidly etch and corrode iron cutting-

tools and iron equipment.


Speck formation and pitch problems during puling and bleaching. Chemical conversions of extractives o colored specks should

therefore involve first a conversion during cooking and then a second one during bleaching. Based of this assumption, methyl p-coumarate was first isolated as one of the major compounds responsible for the specks

Colored oligomer

buteinferruginol aurone

Some Extractives from Wood Causing the Pitch Problems

David Wang’s Wood Chemistry Class -...

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