Yield tropical conditions

When warmed with barium hydroxide, dilute alkalis or acids, hyoscin is hydrolysed, yielding tropic acid and a new base, CgHjsOjN, oscine o scopoline. Depending on the conditions of experiment, the tropic aci obtained may be either the pure Z-form or the partially racemised acid but the oscine obtained is invariably inactive. 

A further outstanding property of poly(methyl methacrylate) is its good outdoor weathering, in which respect the material is markedly superior to most other thermoplastics. After several years under tropical conditions the colour change is extremely small. When poly(methyl methacrylate) is heated above the glass transition temperature (105 C) it becomes rubbery and sheet material is easily manipulated at 150—160 C. Above about 200 C decomposition becomes appreciable and at 350—450 C a nearly quantitative yield of monomer is readily obtained. Thus the recovery of monomer from scrap polymer is a feasible proposition. 

There are approximately 8,750,000 acres of cotton grown in the tropical Americas. This means that under average planting conditions about 127,000 tons of seed are required, which if adequately treated would require about 265.5 tons of protectant chemicals. As the cost of seed treatment is reasonable, the farmers could well afford the extra cost as an added insurance of a uniform stand from the first planting. In general, the highest yields are obtained in areas of the tropics where there has been an active research program. 

Soil 2,4,5-Trichlorophenol and 2,4,5-trichloroanisole were formed when 2,4,5-T was incubated in soil at 25 °C under aerobic conditions. The half-life under these conditions was 14 d (McCall et al, 1981). When 2,4,5-T (10 pg), in unsterilized tropical clay and silty clay soils, was incubated for 4 months, 5 to 35% degradation yields were observed (Rosenberg and Alexander, 1980). Hydrolyzes in soil to 2,4,5-trichlorophenol (Somasundaram et al., 1989,1991) and 2,4,5-trichloroanisole (Somasundaram et al, 1989). The rate of 2,4,5-T degradation in soil remained unchanged in a soil pretreated with its hydrolysis metabolite (2,4,5-trichlorophenol) (Somasundaram et al., 1989). 

In an enantioselective synthesis of a key intermediate for the preparation of poisons from the skin of tropical frogs, a key oxidation was performed under Swern conditions with 77% yield, while PCC provided a 28% yield and Pfitzner-Moffatt oxidation 73% yield. 

Atropine can be synthesized from tropi-none and tropic acid as starting materials. Tropinone can be prepared by Robinson s synthesis (68) and reduced under proper conditions to tropine. ( )-Tropic acid can be prepared from ethyl phenylacetate (69, 70) or acetophenone (71). The 0-acetyl derivative of tropyl chloride reacts with tropine to yield O-acetyl of atropine hydrochloride, from which the acetyl group hydrolyzes spontaneously in aqueous solution (72). 

Intramolecular electrophilic substitution of a pyrrole by a nitrile under acidic conditions generates a dihydropyrrolizine after hydrolysis of the iminium ion intermediate. This type of cyclization has received considerable attention. Braunholtz et al. demonstrated that improved yields (70%) in the cyclization step were effected with a melt of the chlorides of aluminum, potassium, and sodium, but the conditions were extremely critical. Meinwald and Meinwald used this method for their preparation of the dihydropyrrolizinone (50). This confirmed the structure of the major component of the hairpencil secretion of the male tropical butterfly Lycorea ceres ceres. None of the isomeric 2-methyl compound was formed during this synthesis [Eq. (17)]. It is suggested that the 3-methyl group of pyrrole activates the adjacent 2-position sufficiently to promote regiospecific intramolecular electrophilic substitution. 

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