Bark

CfiHi 05 0 C6H4 CH20H. Colourless, bitter crystals, m.p. 20 PC soluble in water and alcohol, insoluble in chloroform. It occurs in the leaves, bark and twigs of species of willow and poplar. On oxidation with dilute nitric acid it is converted into helicin, the glucoside of salicylaldehyde, which has been made the starting point of further syntheses. Gives populin with benzoyl chloride. 

Never use unprotected bark corks for an apparatus ih which a carefully dried liquid is to be distilled, etc., as these corks always contain appreciable quantities of water, which is exuded when the cork comes into contact with a hot liquid. Rubber stoppers should therefore be used in these circumstances. 

Pearson, J.R. A., 1985. Mechanics of Polymer Processing, Applied Science Publishers, Barkings, Essex, UK. 

Rubber stoppers are frequently employed in the laboratory in vacuum distiUation assemblies (compare Section 11,19) for distillations under atmospheric pressure bark corks are generally used. Many organic liquids and vapours dissolve new rubber stoppers slightly and cause them to swell. In practice, it is found that rubber stoppers which have been previously used on one or two occasions are not appreciably attacked by most organic solvents, owing presumably... 

Higher alcohols. These may be purified by drying with anhydrous potassium carbonate or with anhydrous calcium sulphate, and fractionated after filtration from the desiccant. Bark corks (or ground glass joints) should be used rubber stoppers are slightly attacked. The boiUng points of the fractions to be collected are as follows —... 

Review Problem 13 This odd looking molecule (TM 169) is closely related to multistriatin, a phenomone of the elm bark beetle, the insect which spreads Dutch ehn disease. How would you synthesise a sample for testing on the beetle ... 

Benzoic acid had been known for several hundred years by the time of Mitscher lich s experiment Many trees exude resinous materials called balsams when cuts are made m their bark Some of these balsams are very fragrant which once made them highly prized articles of commerce especially when the trees that produced them could be found only m exotic faraway lands Gum benzoin is a balsam obtained from a tree that grows m Java and Sumatra Benzoin is a word derived from the Erench equivalent benjoin which in turn comes from the Arabic luban jawi meaning incense from Java Benzoic acid is itself odorless but can easily be isolated from gum benzoin... 

The first breakthrough came m 1911 when Richard Willstatter prepared cyclooc tatetraene by a lengthy degradation of pseudopelletienne a natural product obtained from the bark of the pomegranate tree Today cyclooctatetraene is prepared from acetylene m a reaction catalyzed by nickel cyanide... 

The fungus responsible for Dutch elm disease is spread by European bark beetles when they burrow into the tree Other beetles congregate at the site attracted by the scent of a mixture of chemicals some emitted by other beetles and some coming from the tree One of the compounds given off by female bark beetles is 4 methyl 3 heptanol Suggest an efficient synthesis of this pheromone from alcohols of five carbon atoms or fewer... 

Alkaloid of cinchona bark used to treat malaria)... 

Phlonzm is obtained from the root bark of apple pear cherry and plum trees It has the molecular formula C21H24O10 and yields a compound A and D glucose on hydrolysis in the pres ence of emulsin When phlorizin is treated with excess methyl iodide in the presence of potassium carbonate and then subjected to acid catalyzed hydrolysis a compound B is obtained Deduce the structure of phlorizin from this information... 

Bitrex Bitter acids Bitter ale Bitter almond oil Bitter bark Bitter magnet... 

K. W. AHen, ed., Fidhesion Vols. 1—14, Elsevier Science Publishers Ltd., Barking, UK, Latest volume is 1990. An annual volume containing recendy presented research results. 

The pomegranate alkaloids, pelletierine (46) and pseudopelletierine (48) as well as minor accompanying bases, have a long history as salts of tannic acid as an anthelmintic mixture for intestinal pinworms (see Antiparasitic AGENTS, ANTHELMINTICS). The alkaloids themselves (as the taimates) are obtained from pomegranate tree (Punkagranatum L.) root bark and are among the few bases named after an individual (P. J. Pelletier) rather than a plant. 

Yohimbine (104), also from the bark of C.johimbe K Schum. and from the roots of R. serpentina (1. ) Benth. has a folk history (unsubstantiated) of use as an aphrodisiac. Its use has been confirmed experimentally as a local anesthetic, with occasional employment for rehef ia angiaa pectoris and arteriosclerosis, but is frequently contraindicated by its undesired renal effects. Yohimbine and some of its derivatives have been reported as hahuciaogenic (70). In addition, its pattern of pharmacological activities ia a variety of animal models is so broad that its general use is avoided. All ten carbon atoms of secologanin (102) as well as the entire skeleton of tryptamine (98, R = H) are clearly seen as iatact portions of this alkaloid. 

Vegetable fibers are classified according to their source ia plants as follows (/) the bast or stem fibers, which form the fibrous bundles ia the inner bark (phloem or bast) of the plant stems, are often referred to as soft fibers for textile use (2) the leaf fibers, which mn lengthwise through the leaves of monocotyledonous plants, are also referred to as hard fibers and (J) the seed-hair fibers, the source of cotton (qv), are the most important vegetable fiber. There are over 250,000 species of higher plants however, only a very limited number of species have been exploited for commercial uses (less than 0.1%). The commercially important fibers are given ia Table 1 (1,2). 

Retting. The removal of the bast fibers from bark and woody stem parts is promoted by a biological treatment called retting (rotting). This is an enzymatic or bacterial action on the pectinous matter of the stem. After retting, the bundles are dried iu fields. Retting may be carried out iu several ways. 

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