ISSN:
0022-3832
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
Relationships between organic compounds of silicon and carbon are based, in large part, upon the facts that the two elements have the same normal covalence and bonding orbitals, but different atomic weights, covalent radii, electronegativity, and maximum covalence. Similarities are most noticeable in the physical properties; and differences, in the chemical properties of analogous compounds of the two elements. One of the most outstanding chemical differences is seen in the high reactivity of bonds between silicon and electronegative elements when compared with similar bonds to carbon. The silicon halides are much more readily hydrolyzed than are analogous carbon halides, and the two types may hydrolyze by different mechanisms. In the hydrolysis of carbon of carbon halides the importance of bond breaking almost always equals, and frequently far exceeds, that of bond making. In the hydrolysis of silicon halides, however, exactly the reverse is true. The greater size of the silicon atom is illustrated by the case of formation of such compounds as tetraphenylsilane and hexaphenyldisilane, but the unreactivity of silicon compounds containing α-substituted groups shows that steric interference between groups attached to silicon does occur. Well-authenticated compounds containing silicon-silicon or silicon-carbon double bonds are unknown, and evidence that resonance contributions from such structures are small is found in the facts that siliconium ions are not formed from triarylsilanols by acid, hexaaryldisilanes do not dissociate into free radicals, and the retarding effect of the p-dimethylamino group is less in the hydrolysis of triarylsilanes than in the hydrolysis of ethyl benzoates.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pol.1952.120090307
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