Gutta perclia


Consider a sphere of air which is carried upward over a distance from Z, to Z2 in the atmosphere. This parcel travels through a region of decreasing pressure, and consequently expands. The expansion requires work, and the air sphere temperature drops. Since the process is usually reasonably rapid, it is a good approximation to assume that this process occurs adiabatically. If the atmospheric lapse rate were exactly the adiabatic lapse rate, then the parcel of air would reach its new position, Zj, at the same temperature as the surroundings, and there would be no buoyant force. We consider this process as having a neutral stability, a displaced mass of air neither tending to return to its original position nor tending to continue its displacement.  [c.283]

In 1981 MaUinckrodt was the only U.S. manufacturer of pyrogaHol via decarboxylation of plant-derived gaHic acid, but it has since ceased production. Harshaw Chemical (Europe) makes pyrogaHol by the same process. Because of the continuing uncertainties of supply of plant materials for gaHic acid—pyrogaHol manufacture, and because of valuable uses for pyrogaHol, there is much interest in the development of synthetic processes. GaHic acid (7) can be made, presumably in good yield, by the sodium alkoxide-catalyzed condensation of a tricarbaHyUc ester with an acetal of mesoxaUc ester, eg, diaLkyl(ethylenedioxy)malonate, via substituted cyclohexane-1,2,3-triones (9).  [c.377]

Resorcinol can be hydroxylated with 50 wt % hydrogen peroxide in the presence of hexafluoroacetone at ca 60°C to give a mixture of pyrogaHol and 1,2,4-trihydroxybenzene (10). The hydrolysis of 2,6-diamino-4-/-butylphenol with aqueous hydrochloric acid at 250°C for 8 h in a pressure reactor provides a 48% yield of pyrogaHol and a 9% yield of 5-/-butylpyrogaHol (11). PyrogaHol or 5-aLkylpyrogaHols can be prepared from 2,6-dibromophenol or 4-aLkyl-2,6-dibromophenol by treatment with sodium methoxide. The 2,6-dimethoxyphenols produced are subjected to ether cleavage with dealkylation in the case of 4-/-butyl-2,6-dimethoxyphenol with aqueous 48 wt % hydrobromic acid to give pyrogaHol in good yield (12).  [c.377]

An adhesive with good peel strength and soldering tolerance for copper in printed circuits is based on a mixture of poly(vinyl butyral) and a modified melamine resin containing pyrogaHol (40). A mbberized pyrogaHol—formaldehyde adhesive improves the adhesion of mbber to nylon (41). PyrogaHol 1-methyl, 3-propyl or aHyl ethers are useful in natural smoke-aroma compositions for food or tobacco (42). PyrogaHol-1,3-dimethyl ether imparts a bonito-like aroma to dried fish (43). Zinc or chrome-plated steel is treated with aqueous pyrogaHol or gaHic acid to improve the adhesion of a final alkyd  [c.377]

Colchiciae (23) is a toxic substance occurring ia Colchicum autumnale, it coataias the aucleus of pyrogaUol trimethyl ether. Colchiciae has beea used ia the treatmeat of acute gout, and ia plant genetics research to effect doubling of chromosomes.  [c.379]

Hydroxyhydroquinone and pyrogaHol can be used for lining reactors for vinyl chloride suspension polymerization to prevent formation of polymer deposits on the reactor walls (98). Hydroxyhydroquinone and certain of its derivatives are useful as auxiUary developers for silver haUde emulsions in photographic material their action is based on the dye diffusion-transfer process. The transferred picture has good contrast and stain-free highlights (99). 5-Acylhydroxyhydroquinones are useful as stabilizer components for poly(alkylene oxide)s (100).  [c.381]

A more recent class of magenta dye-forming couplers is the pyrazolo-(3,2,- )-5-triazoles (11) and related isomers (87) where X can be Cl, SR, S-aryl, or O-aryl. Dyes from this class of couplers are exceedingly attractive, having good thermal stabiHty and much lower unwanted blue and red absorptions than dyes from the pyrazolinones. However, the high piC values of the four-equivalent parents translate into unacceptably low reactivity. Two-equivalent analogues having chloro or aryloxy leaving groups and hydrophilic groups elsewhere in the molecule provide good reactivity and dye yield with resistance to ambient formaldehyde and dyes that do not require post-process stabilization (88). A related class of pyrazolotriazoles (12) is reported to yield dyes having improved light stabiHty (89). The higher piC values of the pyrazolotriazole couplers have led to concerns over image variabiHty induced by small changes in developer pH.  [c.477]

Dipole moments and total energies for pyrazolo[l,5-h]-s-triazole tautomeric forms 97a-97c were calculated using CNDO/2 and CNDO/S (76T341) the results predict the stability of tautomers in a 97a > 97b > 97c sequence. So far, no ab initio calculations or synthesis of 97 have been reported. For pyrazolo[3,2-c]-s-triazole 98 (76T341), the calculated dipole moments, electronic absorption, and proton chemical shifts are in a good  [c.84]


See pages that mention the term Gutta perclia : [c.113]    [c.36]    [c.1480]    [c.1637]    [c.205]    [c.90]    [c.92]    [c.109]    [c.116]    [c.118]    [c.122]    [c.126]    [c.133]    [c.141]    [c.65]    [c.65]    [c.207]    [c.86]    [c.242]   
Organic chemistry (0) -- [ c.408 ]