Abietic acid structure

Rosin and tall oil-based tackifiers are derived from feedstock, which is typically obtained by extraction and distillation of the materials from shredded tree stumps or wood chips. A typical structure of one of the different products obtained through this process is this abietic acid structure shown in Fig. 14 as a representative of the rosin acid family. 

About 80% of the diterpene acids of the genus Finns have an abietane skeleton, with abietic acid (structure 3) as the predominant component. Other diterpene acids have a pimarane skeleton (structure 4). All compounds with the abietane skeleton are distinguished by the presence of an isopropyl group. 

Most of the inhibitors in use are organic nitrogen compounds and these have been classified by Bregman as (a) aliphatic fatty acid derivatives, b) imidazolines, (c) quaternaries, (d) rosin derivatives (complex amine mixtures based on abietic acid) all of these will tend to have long-chain hydrocarbons, e.g. CigH, as part of the structure, (e) petroleum sulphonic acid salts of long-chain diamines (preferred to the diamines), (/) other salts of diamines and (g) fatty amides of aliphatic diamines. Actual compounds in use in classes (a) to d) include oleic and naphthenic acid salts of n-tallowpropylenediamine diamines RNH(CH2) NH2 in which R is a carbon chain of 8-22 atoms and x = 2-10 and reaction products of diamines with acids from the partial oxidation of liquid hydrocarbons. Attention has also been drawn to polyethoxylated compounds in which the water solubility can be controlled by the amount of ethylene oxide added to the molecule. 

Terpenoids are susceptible to a number of alterations mediated by oxidation and reduction reactions. For example, the most abundant molecule in aged Pinus samples is dehydroabietic acid [Structure 7.10], a monoaromatic diterpenoid based on the abietane skeleton which occurs in fresh (bleed) resins only as a minor component. This molecule forms during the oxidative dehydrogenation of abietic acid, which predominates in rosins. Further atmospheric oxidation (autoxidation) leads to 7-oxodehydroabietic acid [Structure 7.11]. This molecule has been identified in many aged coniferous resins such as those used to line transport vessels in the Roman period (Heron and Pollard, 1988 Beck et al., 1989), in thinly spread resins used in paint media (Mills and White, 1994 172-174) and as a component of resin recovered from Egyptian mummy wrappings (Proefke and Rinehart, 1992). 

Tall oil is made up mostly of resin acids with around 10% of neutral components. These resin acids are isomers or structurally close relatives of abietic acid (Figure 2.9) and are used as antislip agents, as a chemical feedstock and as paper-sizing agents (see Chapter 7). 

Figure 2.9 The molecular structure of abietic acid—the dominant component of wood rosin.

Composition. Rosin is primarily a complex mixture of monocarboxylic acids of alkylated hydrophenanthrene nuclei. These constituents, known as resin acids, represent about 90% of rosin. The resin acids are subdivided into two types, based on their skeletal structure. The abietic-type acids contain an isopropyl group pendent from the carbon numbered 13. The pimaric-type acids have a methyl and vinyl group pendent from the same carbon atom. Figure 1 shows the structure of typical resin acids abietic acid, C20H30O2 (1) is predominant. The remaining 10% of commercial rosin consists of neutral materials that are either hydrocarbons or saponifiable esters. These materials are derived from resin acids by decarboxylation or esterification. 

Head-to-tail rearrangement of four isoprene units results in the formation of diterpenes (C20H32), as seen also in Fig. 4.2. Diterpenes are generally found in resins, e.g. pimaric acid and abietic acid. Some diterpenoids are also constituents of essential oils, e.g. phytol [3, 7-14, 37, 52, 53]. Like sesquiterpenes, diterpenes are heavier than monoterpenes therefore, they require more energy to go to the vapour phase. For this reason, longer distillation times are necessary for their recovery. The DNP lists 118 different structural types for diterpenoids [37]. Important diterpenes found in essential oils will be detailed. Some representatives of volatile diterpenes are as in Structure 4.32. 

The isoprene unit exists extensively in nature. It is found in terpenes, camphors, diterpenes (eg, abietic acid), vitamins A and K, chlorophyll, and other compounds isolated from animal and plant materials. The correct structural formula for isoprene was first proposed in 1884 (7). 

On aging, and more rapidly on heating, abietic acid is oxidized first by disproportionation (i.e., without need of oxygen) to dehydroabietic acid (structure 1) and then (but only if exposed to oxygen) to 7-ketodehydroabietic acid (structure 2). The skeletal frequencies of dehydroabietic acid lie at 1110, 1130, and 1175 cm"1 (14),... 

The GC data confirmed the TLC results. TLC detected abietic acid in sample 7 but not in samples 1, 10, and 12. This result indicates that a resin acid concentration of 1% is below the limit of detectability by TLC. TLC revealed dehydroabietic acid in all four samples, and this result was confirmed by GC. The GC data also corroborated the utility of IR spectroscopy. IR spectra showed the isopropyl structure in all four samples, including those for which the acid fraction was less than 10% (samples 10 and 12). Clearly, these isopropyl bands are not from the small amount of residual acid but are caused by skeletal absorptions of the isopropyl group in decarboxylated neutral decomposition products. 

Abietane skeleton, 375, 378 Abietic acid disproportionation, 375 loss in manufacture of pine pitch, 377 oxidation, 375 structure, 371... 

To further complicate the picture, chemical additives are often not pure compounds but mixtures of related structures. The name or chemical designation of the additive often represents only the primary or most abundant chemical structure present. For example. Fig. 1 shows a chromatogram from the analysis by gas chromatography/mass spectrometry (GC/MS) of Abietic Acid, which is an organic chemical filler used in certain types of rubber. The molecular structure of Abietic Acid (I) is ... 

Fig. 1 Chemical structures of abietic acid and dehydroabietic acid.

Diterpenes have, by definition, 20 carbon atoms in their structure. This means that very few are sufficiently volatile to possess an odour. One diterpene is used in perfumery because it and the derivatives concerned are odourless. That is, they are used as solvents. In view of their hydrophobicity and low volatility, these solvents also have fixative properties. Abietic acid is a major component of tall oil, the residue from distillation of turpentine. Esterification and hydrogenation produces two solvents, as shown in Scheme 4.36. 

The Chemistry of Rii c.— The structure and stereochemistry of the various dihydroabietic acids has been clarified. Direct reduction of abietic acid (58), by either catalytic or chemical means, can give rise to products of 1,2- or... 

Tagat et al. reported an approach to SDB as illustrated in Fig. (6). They used commercially available abietic acid 50 structurally similar to SDB especially at carbon 4, 5 and 10 as a starting material. Tricyclic enone 51 was prepared according to the method reported previously by Abad et al. [44] with slight modification. To construct D-ring, intramolecular alkylation of the homonuclear diene 52, readily accessible from 51, was carried out to afford g-alkylated enone 53. Methylation of the enone 53 with LDA/THF at -78°C and Mel followed by ozonolysis gave the 12-methyl enone 54. After selective reduction of the side chain of 54 with Na(OAc)3BH, the mesylate 56 obtained from alcohol 55 was converted to... 

The phenanthrene and chrysene structures could be derived from cyclic terpenoids such as abietic acid, sterols, and hopanes (34). Although tri-phenylene, which has the highest resonance energy among the four-ring catacondensed PAHs (35), was not present in the SRC II HD at a significant level, this compound was found in the coal tar which is a higher temperature... 

Turpentine, which is the sap of coniferous trees, contains in addition to terpenes a non-volatile compound of unknown structure, called abietic anhydride. When the sap is distilled with steam, there are obtained oil of turpentine and abietic acid, C19H28O2, which is non-volatile when the distillation is made without steam the residue is called rosin or colophony. Pinene is the fraction of oil of turpentine which boils at 156° it has the specific gravity 0.86 at 25°. Pinene is present in the oils of rosemary, lemon, sage, juniper, thyme, and anise, and in other essential oils. The structural formulas assigned to pinene is as follows —... 

The 1-and 9-hydroxyl groups define an important area for forskolln s action. The 1,9-dideoxyderlvative (7 ) is totally Inactive and the 1,9,6,7-dicarbonate ( ), and 1,9 sulfonate are very weak at activating adenylate cyclase. Other structurally related compounds which are unable to activate adenylate cyclase are 1,6-dlketoforskolin, the 14,15-oxide (12), virescenol-B, abietic acid, podocarpic acid, retene, glbberellln, and other diterpenes(13-15).23,83 Mone of the inactive dlterpenes antagonize forskolln stimulation of adenylate cyclase. Derivatives of... 

Abietanes. Structural type of diterpenes, e. g., abieta-7,13-diene, the most important representative is abietic acid. 

Analysis of tricyclic alkanes has been less reported in the literature, in comparison with mono-, di-, tetra- and penta-cyclics. However, since we intend to review also separation of fossil fuels, we have to mention compounds such as fichtelite (C19H34) and other diterpenoid tricyclics derived from abietic acid. Abietic acid and levopimaric acid belong to the resin acids, which exude from incisions of bark or trunk of high plants. The derived hydrocarbons, such as fichtelite, were found in the saturated fraction of peat bed extractions. The identification and structure elucidation of fichtelite was based on m.p. 46.5 °C and optical activity [a]D = 18°, as well as on its resistance to chemical attack... 

The C20H36 tricyclic diterpanes are also called diterpane resins, derived from the abietane skeleton. Fichtelite (C19H34), which belongs to the same family, is presumed to be the result of decarboxylation of the abietic acid. The MS of these relate to individual structures (see Figure 10a-e ). 

Figure 7.18. Chemical structures of (a) abietic acid, which is one of the more common constituents of rosin (b) alkyl ketene dimer (AKD), with R = C14-C18 (saturated or unsaturated) (c) alkenyl succinic anhydride (ASA) with R = C14-C18 (unsaturated)...

Similar chromane structures (Fig. 4.13) can also be prepared by the reaction of abietic acid with diphenylolpropane [34]. 

On a different approach, poly(4-abietylmethylstyrene) was prepared in high yields by the reaction of poly (4-chloromethylstyrene) with sodium abietate. Near-UV irradiation of this novel polymer induced its crosslinking by photodimerization through the conjugated double bonds of the abietate moieties [110], presumably by the formation of dimeric structures similar to those described in Fig. 4.15. Abietic acid dimers were also used as diacids in the synthesis of polyamides by reaction with diamines [111]. 

Dehydroabietic acid is a natural product isolated from Pinuspalustris. It is structurally related to abietic acid, wbicb comes from rosin. Tbe synthesis of dehydroabietic acid (/. Am. Chem. Soc. 1962, 84, 284—292) was accomplished by Gilbert Stork. In the course of this synthesis, Stork discovered his famous enamine reaction. 

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