Functional group multiple bonds

Before we start with a systematic discussion of the syntheses of difunctional molecules, we have to point out a formal difficulty. A carbonmultiple bond is, of course, considered as one functional group. With these groups, however, it is not clear, which of the two carbon atoms has to be named as the functional one. A 1,3-diene, for example, could be considered as a 1,2-, 1,3-, or 1,4-difunctional compound. An a, -unsaturated ketone has a 1.2- as well as a 1,3-difunctional structure. We adhere to useful, although arbitrary conventions. Dienes and polyenes are separated out as a special case. a, -Unsaturated alcohols, ketones, etc. are considered as 1,3-difunctional. We call a carbon compound 1,2-difunctional only, if two neighbouring carbon atoms bear hetero atoms. 

Formation and Elimination of Multiple Bond Functionalities. Reactions that involve the formation and elimination of multiple bond functional groups may significantly effect the color of residual lignin in bleached and unbleached pulps. The ethylenic and carbonyl groups conjugated with phenoHc or quinoid stmctures are possible components of chromophore or leucochromophore systems that contribute to the color of lignin. 

This type of cyclization is important only for the formation of cinnolines. In all cases, the starting compounds have an ortho amino group, which upon diazotization undergoes ring closure with the other functionality, most frequently with a multiple bond. 

Functional Groups with Carbon-Carbon Multiple Bonds... 

Functional groups are either attached to the carbon backbone of a molecule or form part of that chain. Examples are the chlorine atom in chloroethane, CH3CH2CI, and the OFF group in ethanol, CFF CI OFi. Carbon-carbon multiple bonds, such as the double bond in 2-butene, are also often considered functional groups. Table 19.1 lists the most common functional groups. Double and triple carbon-carbon bonds were considered in Chapter 18. In the following eight... 

In reality all carbon atoms share equally the pool of electrons which constitute the double bonds and benzene resists addition across the double bonds which would otherwise destroy its unique structure and stability. Single or multiple hydrogen atoms can be substituted to form a host of derivatives containing similar functional groups to those above, e.g. saturated and unsaturated aliphatic chains, amino, carboxylic acidic, halogeno, nitro, and sulphonic acid groups as shown in Table 3.6. 

Reduction of Carbon-Carbon Multiple Bonds, Carbonyl Groups, and Other Functional Groups... 

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