Transcript Extractives
Wood Chemistry PSE 406 Lecture 12 Wood Extractives PSE 406 Lecture 12 1 Agenda General Extractives Information – – – – Classes Chemistry Occurrence Uses PSE 406 Lecture 12 2 Tree Extractives (1) Besides the big three wood compounds, trees contain other compounds that serve a variety of functions including: » Protection (from insects, animals, and rot). » Attractants (flowers, fruits) » Food storage The amount of extractives in wood can range from 120% (species, position in the tree, season, geographical location) More in heartwood PSE 406 Lecture 12 3 Tree Extractives (2) Extractives add significant properties to wood: » Color » Odor » Density These compounds are typically present in very limited amounts but still affect the wood properties greatly. PSE 406 Lecture 12 4 Protection Chemicals Here is a list of the classes of extractives that can serve to protect the tree. » » » » » » » Terpenes Resin Acids Flavonoids Lignans Stilbenes Tannins Phenolics PSE 406 Lecture 12 5 “Other Extractives” These extractives are in the tree typically for reasons other than protection. » » » » Fats and fatty acids Proteins Flavonoids Sterols PSE 406 Lecture 12 6 The Fragrance of a Tree Each tree has a unique fragrance. » Some have strong fragrances than others like Cedar. » Some have only light odor. The aroma is due to volatile compounds produced by the tree (the odor chemicals become gases easily). These chemicals can be isolated and sold. PSE 406 Lecture 12 7 General info End use: » Pine pitch and resins (waterproof boats, in torches and binders). » Medicine, etc. Monomers, dimers, polymers. Softwood have higher extractive content than hardwood. Might be poplar (water) or non-polar solvent (toluene, ethanol, or ether) soluble. More extractives in bark compared to whitewood. PSE 406 Lecture 12 8 Pitch Chemicals When you grab a softwood tree and your hand sticks to the tree, you have discovered pitch. Pitch consists of about 50/50 terpenes and resin acids. Resin acids are glassy like chemicals also made of isoprene units. PSE 406 Lecture 12 9 Pitch as a Bandage When a softwood tree is wounded, it releases pitch to “seal” the wound. » Terpenes serve as the antiseptic and then evaporate. » Resin acids serve as the bandage (and also as an antiseptic). PSE 406 Lecture 12 10 Sterols Role in Nature Sterols are found in plants as both free sterols, as sterol esters (of fatty acids) and as sterol glycosides Serve as components of membranes » Work with phospolipids to create membranes which are only permeable to certain chemicals Sterol esters » Believed to serve as transport agent to get sterols from site of biosynthesis to membrane PSE 406 Lecture 12 11 What are Fats and Oils? Fat and oils are energy storage material. Fats and oils are similar chemically: the difference is that fats are solids at room temperature and oils are liquids. PSE 406 Lecture 12 12 Chemical Composition of Fat/Oils Esters of long chain fatty acids » Most often with glycerol Trigylcerides, diglycerides, & monoglycerides Similar structures in all plants. What varies is the fatty acids attached to the glycerol and the percentage of tri, di, and monoglycerides H2C O CO R1 H2C O CO R1 H2C O CO R1 H 2C O CO R2 H2C O CO R2 H H H2C OH H2C O CO R3 H2C OH H2C OH Diglyceride Triglyceride Monoglyceride O H2C O C PSE 406 Lecture 12 13 Chemical Composition of Fatty Acids Fatty acids are long chained carboxylic acids » Mostly even numbered chains – 16-18 carbons most common – 20-22 less common » 80% unsaturated: 1, 2 or 3 double bonds Secondary Fatty Acids Major Fatty Acids COOH COOH Palmitic acid (C16) Oleic acid (C18) COOH COOH Linolenic acid (C18) COOH Linoleic acid (C18) Eicosadienoic acid (C20) PSE 406 Lecture 12 14 Fat (Oil) Content There are high levels of fats in seeds. » Corn and soybeans contain 10-20% oils. » Canola and sunflower contain up almost 50% oils. » Nuts 50-70% oils In agricultural crops the majority of the oils are triglycerides. PSE 406 Lecture 12 15 Fats in Trees Fats are found in living cells - parenchyma » Very low content (1-2%) in oleoresin. » More present in sapwood than heartwood. » High content in many nuts. Function » Fats role in trees is the same as in your waist line: serves as a storage material. » The amount of fat in the tree is seasonally dependent. PSE 406 Lecture 12 16 Waxes Wax is the water resistant protective coatings of leaves, fruits, and trees (bark). Wax is a mixture of a variety of different chemicals. » Waxes consist mainly of very long chained (C12-38) fatty acid esters of long chained alcohols. Waxes CH3 (CH2)n O CO (CH2)m CH3 C20H41OH C24H49OH PSE 406 Lecture 12 Arachidic Alcohol Lignoceric Alcohol 17 Flavonoids OH OH Serve many roles in plants: O HO OH » Protection » Coloration » Other unique roles. OH Catechin (Western Hemlock) PSE 406 Lecture 12 18 Flavonoids Location in Tree Found in the heartwood of most tress » Often responsible for coloration Found in lesser amounts in the sapwood Are found in large amounts in bark and roots Leaves: green tea can contain up to 30% flavonoids Flowers: color is often due to flavonoids PSE 406 Lecture 12 19 Flavonoids Medicinal Uses Higher flavonoid content in diet reduces chance of: » Heart Disease – Strengthen capillaries – Dilates blood vessels » Stroke » Cancer: all types reduced – Finnish study = ½ rate of cancer PSE 406 Lecture 12 20 Condensed Tannins Biological Significance Western hemlock » Bark: 18% tannins, wood: 2% tannins » Chestnut and oak Protection of plants against insects/animals » Bad Taste (bitter taste) Toxic to bacteria Uses of condensed tannins » Leather tanning: 10,000+ year old industry » Adhesives PSE 406 Lecture 12 21 Alkaloids These nitrogen containing compounds are found in a variety of different plants. » Located in the leaves, fruits, and bark. O N N O N N You are all aware of the Nicotine alkaloids shown on this N page you probably have never seen their structures. These are typically found in small amounts in plants but Cocaine are worth large sums of cash. PSE 406 Lecture 12 N Caffeine O O O O 22