Crystalline solids substitutions

Triphosgene, a safe and stable crystalline solid substitute for phosgene [53, 148], is successfully utilized in the sequential synthesis of unsymmetrical ureas also bearing chiral amino acid derivatives, without any need to purify the intermediates [507]. 

Substituted Ammonium Ions. Like NH4C1 the substance NH3-(CH3JCI, where a CH3 group has been substituted for one hydrogen, forms a crystalline solid and so do the substances NH2(CH3)2C1 and NH(CH3)3C1. When one of these substances is dissolved in water, it is completely dissociated into Cl- ions and molecular positive ions corresponding to (NH4)+. Suppose now that such a solution contains an NH3 molecule, and consider the following proton transfer... 

Polymerization in electrostatic systems like the ones mentioned above is stericaUy inhibited by alkyl substitution at the a-carbon which must assume a coordination number greater than 4. Coates and Glockhng have treated this inhibition of polymerization in terms of decreased electronegative character of the branched alkyl groups. Therefore, stimulated by the idea that f-afkylhthium compounds may exist as low polymers or even as monomeric molecules, Weiner and coworkers and Kottke and Stalke have isolated f-butyllithium as a pure substance for the first time and characterised it by spectroscopic methods and X-ray diffraction. The colourless crystalline solid was found to be tetrameric over a range of concentrations in both benzene and hexane ... 

Benzotriazine (8, R = H), for example, can be isolated as a reasonably stable, colorless crystalline solid, but it reacts rapidly in solution with water to give o-aminobenzaldehyde, presumably by initial covalent hydration to give 98, which decomposes to o-aminobenzaldehyde via the triazene 99. Reaction of 8, R = H, with other nucleophiles also occurs readily, while 4-substituted 1,2,3-benzo-triazines react similarly but more slowly, as expected, owing to a combination of steric and electronic effects. 

Eigure 1.29 Representation of interstitial and substitutional impurity atoms in a crystalline solid. From K. M. Ralls, T. H. Courtney, and J. Wulff, Introduction to Materials Science and Engineering. Copyright 1976 by John Wiley Sons, Inc. This material is used by permission of John Wiley Sons, Inc. 

Acetates. The acetates of monohydric phenols are usually liquids, but those of di and tri-hydric phenols and also of many substituted phenols are frequently crystalline solids. They may be prepared with acetic anhydride as detailed under Amines, Section IV, 100,7. 

This group comprises substances of the type RCONHR and RCONR R",. e., substituted amides of the aromatic series. They are all well-defined crystalline solids, sparingly soluble in cold but, often, appreciably soluble in hot water and moderately soluble in ether they are generally neutral or feebly basic in reaction. 

HEXAMINE. CAS 100-97-0], (CH-),N . formula weight 140,19, white crystalline solid, mp 280rC. decomposes at higher temperatures. Alsu known as hexamethylenetetramine, nicihenuiniiie. and urotiopitie. the compound is soluble in H2O and only very slightly soluble in alcohol or ether. Although used to some extent in medicine as an internal antiseptic, the primary use of hexamine is in the manufacture of synthetic resins where the compound is a substitute for formalin (aqueous solution of paraformaldehyde) and its NaOH catalyst. Hexamine also is used as an accelerator for rubber. 

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