Wood Chemistry Wood Chemistry Pitch Chemicals

l When you grab a softwood tree and your hand sticks to the tree, Wood Chemistry you have discovered pitch. PSE 406/Chem E 470 l Pitch consists of about 50/50 terpenes and resin acids. Resin acids are glassy like chemicals Lecture 13 also made of isoprene units. Diterpenes and Triterpenes l The Christmas tree I’m holding didn’t have any pitch left.

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Wood Chemistry Pitch as a Bandage Wood Chemistry Rosin

l The term rosin refers to a mixture of resin acids l When a softwood tree produced through the distillation of pitch. is wounded, it releases l Gum rosin: distillation of gum resins (wound resin) pitch to “seal” the » US 197 metric tons (1998) wound. l Tall oil rosin: from the Swedish word talloja which » Terpenes serve as the antiseptic and then means pine oil. Produced during the kraft pulping evaporate. process. » Resin acids serve as the » US 247,000 metric tons (1998) bandage (and also as an l Wood rosin: Distillation of old stumps. antiseptic). » US 30,000 metric tons (1998)

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1 1 Wood Chemistry Diterpenes: Structure Wood Chemistry Diterpenes: Structure

l 4 isoprene units linked head to tail l Ring structures l Neutrals: » Hydrocarbons, phenolics, alcohols, ketones and aldehydes » Acyclic, mono, di, tri and tetracyclic l Acids: Typically referred to as resin acids » Macrocylcic (10-15 carbons) l Acid content much higher in heartwood than sapwood

OH

H

COOH H H CH2OH COOH CHO Bicyclic Tricylcic Tetracyclic Macrocyclic Pimarinol Abietic Acid Levopimaral Pimaradiene

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Diterpenes Wood Chemistry Diterpenes: Location in Tree Wood Chemistry Physical Properties

l Composition is very species dependent l Rosin (mixture of diterpenoids) is glass like: it slowly softens when heated – does not have a melting point l Mainly found in conifers (0.2-0.8%) l Pure resin acids are crystalline » Oleoresin: ~70% resin acids (tricyclic/COOH) » Pimaric acid mp = 217-219°C » Heartwood: Large amount of neutral l Tricylcic structure quite stable: Amber diterpenoids that have been modified through l Volatilization various reactions: » Some diterpenoids can be volatilized with steam – Aromatization, hydroxylation, oxidation, & » Problem in TMP plants (health reasons) rearrangements (often losing C atom) l Solubility: Abieticacid l Tropical Hardwoods: – Insoluble in water » Sandalwood: 12-14% resin – Some solubility in base

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2 2 Diterpenes

Wood Chemistry Pulp and Paper Problems Wood Chemistry Uses of Diterpenes

l Toxicity l Rosin: Mixture of » Diterpenoids are primary pollutants in pulp mill resin acids effluents » Gum Rosin » Very toxic to fish » Tall Oil Rosin » Difficult to remove in treatment systems l Uses of Rosin » LD50 not particularly high (abietic 180mg/kg) » Printing Inks, Paper » Inhalation problems in saw mills Size, Rubber, l Stickies Adhesives, Miscellaneous

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Triterpenes & Sterols Triterpenes & Sterols Wood Chemistry Chemical Composition Wood Chemistry Chemical Composition

l 6 isoprene units linked head to tail OH l Many are classified as HO steroids (sterane structure) HO HO

» Triterpenoids and sterols have Serratenediol b-Sitosterol same synthetic pathway so Cholesterol Triterpenes CH3 (not in trees) they should not be separated 6 * 5C » Both start from squalene and then branch off

Squalene HO HO Squalene Campesterol a-Sitosterol

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3 3 Triterpenes & Sterols Triterpenes& Sterols Wood Chemistry Chemical Composition Wood Chemistry Physical Properties

l Triterpenoids exist in three forms b-sitosterol » Free form » Esters of fatty acids l Crystalline » Glycosides » mp 140°C l Can contain a large variety of functional groups l Solubility » Carboxyl » Ethers » Organic solvents: ether, alcohols, etc » Acetyl l Boiling Point » Alcohols » Merck index: no boiling point listed. Found in » Ketones tall oil pitch - does not distill

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Triterpenes & Sterols Wood Chemistry Role in Nature Wood Chemistry Sterol levels in plants

l Sterols are found in plants as both free sterols, as l Levels of sterols variable depending on plant. sterol esters (of fatty acids) and as sterol glycosides » Broccoli: 3.4g/kg l Serve as components of membranes » Banana: 0.5g/kg » Work with phospolipids to create membranes which are » Alfalfa 2.1 g/kg only permeable to certain chemicals » Aspen (wood): 5 g/kg l Sterol esters l Free sterols are found in vegetable oils. » Believed to serve as transport agent to get sterols from » Peanut oil: 1-2 mg/kg oil site of biosynthesis to membrane » Corn oil: 2-4 mg/kg l Sterol glycosides ?????????

•1. J Food Comp Anal 2002 15, 123 •2. TAPPI, 1999 83(5) PSE 406 Lecture 13 15 PSE 406 Lecture 13 16

4 4 Triterpenes & Sterols Triterpenes & Sterols Wood Chemistry Tree Information Wood Chemistry Pulp and Paper Problems

l Found in both hardwoods and softwoods l Sterol esters are difficult to saponify: known as » Not a very large component in softwoods nonsaponifiables » b-sitosterol major component » Some chemical conversions during pulping but mostly » Larger amounts in tropical hardwoods stable. » Large number of reactions during bleaching l Not found to any extent in oleoresin – saponification l Found throughout the tree l Hydrophobic nature of sterol esters cause them to be » Concentration actually higher as go from bark to a major pitch problem in papermaking pith » Major components of pitch deposits – Not involved in heartwood formation – Higher concentration of sterols in younger trees

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Sterols from Trees Sterols from Trees: Wood Chemistry Benecol (1) Wood Chemistry Benecol (2)

l Benecol: cholesterol reducing product. l Sitostanol » Known since 1950s that vegetable sterols can » Similar structure to reduce blood cholesterol. sitosterol – High levels of sterols can cause other problems » Saturated sterol » 1970s shown that plant stanols were effective at » Found in Nordic Pine lowering cholesterol without negative effects. l In Benecol the HO – Stanols not fat soluble so difficult to use. sitostanol is in the form – Finnish company (Rasio) developed a procedure in late of a fatty acid ester. 1980s early 1990s to produce stable fat soluble stanol esters from plant derived sterols.

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