The following sections of this BookRags Literature Study Guide is offprint from Gale's For Students Series: Presenting Analysis, Context, and Criticism on Commonly Studied Works: Introduction, Author Biography, Plot Summary, Characters, Themes, Style, Historical Context, Critical Overview, Criticism and Critical Essays, Media Adaptations, Topics for Further Study, Compare & Contrast, What Do I Read Next?, For Further Study, and Sources.
(c)1998-2002; (c)2002 by Gale. Gale is an imprint of The Gale Group, Inc., a division of Thomson Learning, Inc. Gale and Design and Thomson Learning are trademarks used herein under license.
The following sections, if they exist, are offprint from Beacham's Encyclopedia of Popular Fiction: "Social Concerns", "Thematic Overview", "Techniques", "Literary Precedents", "Key Questions", "Related Titles", "Adaptations", "Related Web Sites". (c)1994-2005, by Walton Beacham.
The following sections, if they exist, are offprint from Beacham's Guide to Literature for Young Adults: "About the Author", "Overview", "Setting", "Literary Qualities", "Social Sensitivity", "Topics for Discussion", "Ideas for Reports and Papers". (c)1994-2005, by Walton Beacham.
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A carbene has a general formula of R2C:. Carbenes are one of the principle groups of reactive organic intermediaries and they are highly reactive due to the two unpaired electrons. Photolysis of a diazoalkane or a simple elimination reaction will produce a carbene. Dihalocarbenes such as Cl2C: have the greatest synthetic value as they frequently act as intermediates in organic syntheses.
Carbenes can act as electron donors in chemical reactions. They are intermediates in such reactions as the change of a carboxylic acid to its next highest homologue or to a derivative of a homologous acid such as an ester or an amide. (A homologous series is a group of organic compounds that have the same functional group and a regular structural pattern so that a member of the series differs from the next member by a fixed number of atoms.) The reaction of a base with a trihalogen derivative of methane is an example of a commonly encountered reaction which proceeds via a carbene intermediate.
Carbenes are so reactive that they are unlikely to be frequently encountered. In any reaction of which they are a part, they rapidly move to the next stage of the synthesis. It is only in reactions with transition metals that carbenes are stable, due to the distribution of electrons within the structure formed.