Resin acid

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Resin acid refers to any of several related carboxylic acids found in tree resins. Nearly all resin acids have the same basic skeleton: three fused rings having the empirical formula C19H29COOH. Resin acids occur in nature as tacky, yellowish gums consisting of several compounds. They are water-insoluble. A common resin acid is abietic acid. [1] Resin acids are used to produce soaps for diverse applications, but their use is being displaced increasingly by synthetic acids such as 2-ethylhexanoic acid or petroleum-derived naphthenic acids.

Contents

Botanical analysis

Resin acids are protectants and wood preservatives that are produced by parenchymatous epithelial cells that surround the resin ducts in trees from temperate coniferous forests. The resin acids are formed when two-carbon and three-carbon molecules couple with isoprene building units to form monoterpenes (volatile), sesquiterpenes (volatile), and diterpenes (nonvolatile) structures.

Pines contain numerous vertical and radial resin ducts scattered throughout the entire wood. The accumulation of resin in the heartwood and resin ducts causes a maximum concentration in the base of the older trees. Resin in the sapwood, however, is less at the base of the tree and increases with height.

In 2005, as an infestation of the Mountain pine beetle (Dendroctonus ponderosae) and blue stain fungus devastated the Lodgepole Pine forests of northern interior British Columbia, Canada, resin acid levels three to four times greater than normal were detected in infected trees, prior to death. These increased levels show that a tree uses the resins as a defense. Resins are both toxic to the beetle and the fungus and also can entomb the beetle in diterpene remains from secretions. Increasing resin production has been proposed as a way to slow the spread of the beetle in the "Red Zone" or the wildlife urban interface.

Chemical components

Biosynthesis and isolation

Resin acids originate from geranylgeranyl pyrophosphate, which is acted on (i.e., the substrate for) by copalyl diphosphate synthase. The initial conversion gives copalyl diphosphate, the progenitor of the diterpene diphosphates (nomenclature warning: pyrophosphate and diphosphate are often used interchangeably). Under enzymatic control, this pyrophosphate compound rearranges into the following diterpenes: levopimaradiene, abietadiene, neoabietadiene. Traces of three other diterpenes are also generated: palustradiene, sandaracopimaradiene, and pimara-8(14),15-diene. These hydrocarbons are substrates for cytochrome P450, which introduces oxygen functionalities, i.e. converts C-H bonds to C-OH bonds and similar reactions involving oxygen in air. This conversion turn terpenes into terpenoids. [1]

Several important resin acids can be identified in rosin, as listed below. [2] The two classes, abietic acids and pimaric acids, are isomers with the formula C19H29CO2H.

Abietic-type acids

The diterpenoid abietic acid, a common resin acid. Abietic acid.svg
The diterpenoid abietic acid, a common resin acid.

Pimaric-type acids

The diterpenoid pimaric acid, a common resin acid. Pimaric acid structure.svg
The diterpenoid pimaric acid, a common resin acid.

Others

Production in tall oil (chemical pulping byproduct)

The commercial manufacture of wood pulp grade chemical cellulose using the kraft chemical pulping processes releases resin acids. The Kraft process is conducted under strongly alkaline conditions of sodium hydroxide, sodium sulfide, and sodium hydrosulfide. These bases neutralize resin acids, converting them to their respective sodium salts, sodium abietate, ((CH3)4C15H17COONa), sodium pimarate ((CH3)3(CH2)C15H23COONa) and so on. In this form, the sodium salts are poorly insoluble and, being of lower density than the spent pulping process liquor, float to the surface of storage vessels during the process of concentration, as a somewhat gelatinous pasty fluid called kraft soap (also called resin soap). [3]

Kraft soap can be reneutralized with sulfuric acid to restore the acidic forms abietic acid, palmitic acid, and related resin acid components. This refined mixture is called tall oil. Other major components include fatty acids and unsaponifiable sterols.

Resin acids, because of the same protectant nature they provide in the trees where they originate, also impose toxic implications on the effluent treatment facilities in pulp manufacturing plants. Furthermore, any residual resin acids that pass the treatment facilities add toxicity to the stream discharged to the receiving waters.

Variation with species and biogeoclimatic zone

The chemical composition of tall oil varies with the species of trees used in pulping, and in turn with geographical location. For example, the coastal areas of the southeastern United States have a high proportion of Slash Pine (Pinus elliottii); inland areas of the same region have a preponderance of Loblolly Pine (Pinus taeda). Slash Pine generally contains a higher concentration of resin acids than Loblolly Pine.

In general, the tall oil produced in coastal areas of the southeastern United States contains over 40% resin acids and sometimes as much as 50% or more. The fatty acids fraction is usually lower than the resin acids, and unsaponifiables amount to 6-8%. Farther north in Virginia, where Pitch Pine (Pinus rigida)and Shortleaf Pine (Pinus echinata) are more dominant, the resin acid content decreases to as low as 30-35% with a corresponding increase in the fatty acids present.

In Canada, where mills process Lodgepole Pine (Pinus contorta) in interior British Columbia and Alberta, Jack Pine (Pinus banksiana), Alberta to Quebec and Eastern White Pine (Pinus strobus) and Red Pine (Pinus resinosa), Ontario to New Brunswick, resin acid levels of 25% are common with unsaponifiable contents of 12-25%. Similar variations may be found in other parts of the United States and in other countries. For example, in Finland, Sweden and Russia, resin acid values from Scots Pine (Pinus sylvestris) may vary from 20 to 50%, fatty acids from 35 to 70%, and unsaponifiables from 6 to 30%.

Uses

Resin acids are converted into ester gum by reaction with controlled amounts of glycerol or other polyhydric alcohols.

Some have drying properties, and as ester gum is used in paints, varnishes, and lacquers. [4]

Resin acids are converted to resin soaps.

Safety

Resin acids are very poorly soluble in water (milligrams per liter) and have low acute toxicity. [5]

Further reading

Related Research Articles

<span class="mw-page-title-main">Resin</span> Organic polymer, typically from plants

A resin is a solid or highly viscous liquid that can be converted into a polymer. Resins may be biological or synthetic in origin, but are typically harvested from plants. Resins are mixtures of organic compounds, and predominantly terpenes. Well known resins include amber, hashish, frankincense, myrrh and the animal-derived resin, shellac. Resins are commonly used in varnishes, adhesives, food additives, incenses and perfumes.

<span class="mw-page-title-main">Turpentine</span> Liquid distilled from pine resin

Turpentine is a fluid obtained by the distillation of resin harvested from living trees, mainly pines. Principally used as a specialized solvent, it is also a source of material for organic syntheses.

<span class="mw-page-title-main">Pinaceae</span> Family of conifers

The Pinaceae, or pine family, are conifer trees or shrubs, including many of the well-known conifers of commercial importance such as cedars, firs, hemlocks, piñons, larches, pines and spruces. The family is included in the order Pinales, formerly known as Coniferales. Pinaceae have distinctive cones with woody scales bearing typically two ovules, and are supported as monophyletic by both morphological trait and genetic analysis. They are the largest extant conifer family in species diversity, with between 220 and 250 species in 11 genera, and the second-largest in geographical range, found in most of the Northern Hemisphere, with the majority of the species in temperate climates, but ranging from subarctic to tropical. The family often forms the dominant component of boreal, coastal, and montane forests. One species, Pinus merkusii, grows just south of the equator in Southeast Asia. Major centres of diversity are found in the mountains of southwest China, Mexico, central Japan, and California.

Rosin, also known as colophony or Greek pitch (Latin: pix graeca), is a resinous material obtained from pine trees and other plants, mostly conifers. The primary components of rosin are diterpenoids, i.e., C20 carboxylic acids. Rosin consists mainly of resin acids, especially abietic acid. Rosin often appears as a semi-transparent, brittle substance that ranges in color from yellow to black and melts at stove-top temperatures.

<span class="mw-page-title-main">Abietic acid</span> Chemical compound

Abietic acid is a diterpenoid found in coniferous trees. It is supposed to exist as a defend the host plant from insect attack or various wounds. Chemically, it is a complicated molecule featuring two alkene groups and a carboxylic acid within a chiral tricyclic framework. As the major component of rosin, it is a commercially important. Historically speaking, it was a major component of naval stores. It is the most common of the resin acids. Another common resin acid is pimaric acid, which converts to abietic acid upon heating.

<i>Pinus rigida</i> Species of pine tree

Pinus rigida, the pitch pine, is a small-to-medium-sized pine. It is native to eastern North America, primarily from central Maine south to Georgia and as far west as Kentucky. It is found in environments which other species would find unsuitable for growth, such as acidic, sandy, and low-nutrient soils.

<i>Pinus koraiensis</i> Species of conifer

Pinus koraiensis is a species of pine known commonly as the Korean pine. It is a relic species of the Tertiary, identified as a rare tree species by United Nations. It is native to eastern Asia: Korea, northeastern China, Mongolia, the temperate rainforests of the Russian Far East, and central Japan. In the north of its range, it grows at moderate elevations, typically 600 to 900 metres, whereas further south, it is a mountain tree, growing at 2,000 to 2,600 m elevation in Japan. Other common names include Chinese pinenut. The ancient woodland of P. koraiensis on the earth is about 50 million hectares, and China has about 30 million hectares, accounting for 60%. It is a second-class national key protected plant in China. P. koraiensis is a tree species with high economic and ecological value. The official name in Chinese is "红松 hóng sōng/red pine", because almost every part of it is related to red.

<span class="mw-page-title-main">Kraft process</span> Process of converting wood into wood pulp

The kraft process (also known as kraft pulping or sulfate process) is a process for conversion of wood into wood pulp, which consists of almost pure cellulose fibres, the main component of paper. The kraft process involves treatment of wood chips with a hot mixture of water, sodium hydroxide (NaOH), and sodium sulfide (Na2S), known as white liquor, that breaks the bonds that link lignin, hemicellulose, and cellulose. The technology entails several steps, both mechanical and chemical. It is the dominant method for producing paper. In some situations, the process has been controversial because kraft plants can release odorous products and in some situations produce substantial liquid wastes.

<i>Pimenta racemosa</i> Species of plant

Pimenta racemosa is a species of plant in the myrtle family (Myrtaceae) that is native to the Caribbean region. Common names include West Indian bay tree, bay rum tree, and ciliment.

<span class="mw-page-title-main">Black liquor</span> Industrial by-product

In industrial chemistry, black liquor is the by-product from the kraft process when digesting pulpwood into paper pulp removing lignin, hemicelluloses and other extractives from the wood to free the cellulose fibers.

Resin soap is a mix of salts of resin acids. It is a yellow gelatinous pasty soap with use in bleaching and cleaning and as a compound of some varnishes. It also finds use in rubber industry as an emulsifier. Often the soap is pretreated with formaldehyde and maleic anhydride.

Tall oil, also called liquid rosin or tallol, is a viscous yellow-black odorous liquid obtained as a by-product of the kraft process of wood pulp manufacture when pulping mainly coniferous trees. The name originated as an anglicization of the Swedish tallolja. Tall oil is the third largest chemical by-product in a kraft mill after lignin and hemicellulose; the yield of crude tall oil from the process is in the range of 30–50 kg / ton pulp. It may contribute to 1.0–1.5% of the mill's revenue if not used internally.

The enzyme abieta-7,13-diene synthase catalyzes the chemical reaction

<span class="mw-page-title-main">Abietane</span> Chemical compound

Abietane is a diterpene that forms the structural basis for a variety of natural chemical compounds such as abietic acid, carnosic acid, and ferruginol which are collectively known as abietanes or abietane diterpenes.

<span class="mw-page-title-main">Levopimaric acid</span> Chemical compound

Levopimaric acid is an abietane-type of diterpene resin acid. It is a major constituent of pine oleoresin with the chemical formula of C20H30O2. In general, the abietene types of diterpene resin acid have various biological activities, such as antibacterial, cardiovascular and antioxidant. Levopimaric acid accounts for about 18 to 25% of pine oleoresin. The production of oleoresin by conifer species is an important component of the defense response against insect attack and fungal pathogen infection.

Abieta-7,13-dien-18-ol hydroxylase (EC 1.14.13.109, CYP720B1, PTAO) is an enzyme with systematic name abieta-7,13-dien-18-ol,NADPH:oxygen oxidoreductase (18-hydroxylating). This enzyme catalyses the following chemical reaction

Levopimaradiene synthase is an enzyme with systematic name (+)-copalyl-diphosphate diphosphate-lyase . This enzyme catalyses the following chemical reaction

Neoabietadiene synthase is an enzyme with systematic name (+)-copaly-diphosphate diphosphate-lyase . This enzyme catalyses the following chemical reaction:

<span class="mw-page-title-main">Palustric acid</span> Chemical compound

Palustric acid is an organic compound with the formula C20H30O2. It is classified as a diterpenoid and a resin acid. Palustric acid is an isomer of abietic acid: the location of the two C=C bonds differ in these two compounds. It is a colorless solid that is soluble in polar organic solvents. In terms of biological function palustric acid protects its host trees, especially conifers, against insects, an example of plant defense against herbivory. It is biosynthesized from the C20 precursor geranylgeranyl diphosphate.

References

  1. 1 2 Keeling, Christopher I.; Bohlmann, Jörg (2006). "Diterpene resin acids in conifers". Phytochemistry. 67 (22): 2415–2423. doi:10.1016/j.phytochem.2006.08.019. PMID   16996548.
  2. Fiebach, Klemens; Grimm, Dieter (2000). "Resins, Natural". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a23_073. ISBN   3-527-30673-0.
  3. Norlin, Lars-Hugo (2000). "Tall Oil". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a26_057. ISBN   978-3-527-30385-4.
  4. Hoiberg, Dale H., ed. (2010). "abietic acid" . Encyclopædia Britannica. Vol. I: A-ak Bayes (15th ed.). Chicago, Illinois: Encyclopædia Britannica Inc. pp.  32. ISBN   978-1-59339-837-8.
  5. Peng, Guomei; Roberts, John C. (2000). "Solubility and Toxicity of Resin Acids". Water Research. 34 (10): 2779–2785. Bibcode:2000WatRe..34.2779P. doi:10.1016/s0043-1354(99)00406-6.