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Purification, general amides

The general theory behind the process is that the hypohalite will convert the amide to a haloamide. This then spontaneously changes to the isocyanate when heated and decomposes to the amine from the water present. In effect, all that happens is that a Carbonyl (CO) group is stripped off the starting amide to yield the corresponding amine. Yields pre- purification are around 80%, post-purification average around 65%. Certain uses of the result-... [Pg.260]

The phenylbenzamide is prepared from the acid chloride in the presence of Et3N (86% yield) and can be cleaved with 3% Na(Hg) (MeOH, 25°, 4 h, 81% yield). Most amides react only slowly with Na(Hg). Phenylbenzamides are generally crystalline compounds, an aid in their purification. ... [Pg.561]

A -( 1-Chloro- or bromoalkyl)amides are generally moisture-sensitive, unstable compounds, which are often directly used without further purification. Standard Lewis acids such as boron trifluoride-diethyl ether, aluminum(lll) chloride, zinc(II) chloride, tin(IV) chloride and titani-um(IV) chloride are used to generate the /V-acyliminium ion, although sometimes a catalyst is not necessary. [Pg.815]

A melting point in the lower part of this range generally indicates contamination with / -tolylsulfonylmethylamide, which may be removed as described in Note 6 however, this purification is not necessary since the presence of this amide does not interfere in the preparation of diazomethane. [Pg.99]

The most accurate method of analysis for serine, threonine and tyrosine in proteins is to hydrolyze the proteins for several different times (e.g. 24, 48 and 72 hr) and extrapolate the values to 0 time. In general, the more times that are utilized, the more accurate will be the extrapolation. Extrapolation of the NHj content of these hydrolysates to 0 time will also give an estimate of the number of amides present in the protein, if care has been used to exclude NHj during purification of the protein. The inclusion of phenol in the hydrolysates has generally decreased the rates of destruction, particularly for tyrosine. If serine phosphate ( 2.12.4) or similar derivatives are present, the extrapolated curve will be more complex due to different rates of destruction. [Pg.18]

The most common procedure for preparing bismuth alkoxides is the substitution reaction of bismuth halides with alkali metal alkoxides. The alternative is treatment of bismuth amides with alcohols. Bismuth alkoxides such as trimethoxide, triethoxide and triisopropoxide were first prepared in 80-93% yields by the reaction between BiCl3 and alkali metal alkoxides by Mehrotra et al. in 1966. Bismuth alkoxides are less soluble in organic solvents and the yields after purification by sublimation are generally very low (10-20%) [66IJC537]. Known aliphatic alkoxides include Bi(OEt)3... [Pg.154]

In 1983, Fehrentz and Castro [86] described an efficient synthesis of optically pure AT-tert-butyloxycarbonyl (Boc)-a-amino aldehydes 3 by reduction of the corresponding A, 6>-dimethylhydroxamates 1 (Weinreb amide [91]) with LiAlH4 at 0°C (Scheme 2). Overreduction to an alcohol is precluded by the formation of an intermediate lithium salt 2 that upon hydrolysis affords the desired aldehyde. Yields are generally excellent and purification on silica gel is not necessary. [Pg.652]


See other pages where Purification, general amides is mentioned: [Pg.554]    [Pg.112]    [Pg.163]    [Pg.115]    [Pg.15]    [Pg.364]    [Pg.554]    [Pg.411]    [Pg.669]    [Pg.67]    [Pg.214]    [Pg.117]    [Pg.212]    [Pg.287]    [Pg.268]    [Pg.1285]    [Pg.331]    [Pg.1285]    [Pg.643]    [Pg.55]    [Pg.232]    [Pg.24]    [Pg.425]    [Pg.27]    [Pg.277]    [Pg.454]    [Pg.391]    [Pg.16]    [Pg.554]    [Pg.154]    [Pg.364]    [Pg.190]    [Pg.204]    [Pg.554]    [Pg.402]    [Pg.268]    [Pg.27]    [Pg.153]   
See also in sourсe #XX -- [ Pg.63 ]

See also in sourсe #XX -- [ Pg.63 ]

See also in sourсe #XX -- [ Pg.82 ]

See also in sourсe #XX -- [ Pg.82 ]




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Amides General

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