Branched-chain alkenes

PdCb-CuCb catalyzes the condensation of branched-chain alkenes with formaldehyde to give the l,3-dioxanes 96a and 96b (Prins reaction)[73]. The yields are much higher than in the conventional acid-catalyzed Prins reaction. 

Branched-chain alkenes react with hydrazine under acidic conditions to give the corresponding alkyl hydrazine. For example, isobutylene bubbled through an aqueous solution of hydrazine and HCl gives /-butyUiydrazine in reasonably good yields (64). 

The major component of the female sex pheromone produced by the herald moth, Scoliopteryx libatrix (L.) (Lepidoptera Noctuidae), has been identified as (6Z)-13-methylheneicosene. This is the first example of a branched chain alkene as a sex pheromone in the Noctuidae family and is markedly different from the pheromones of the other members in the group. The authors have not conclusively stated, but they suggest that it is probably the (Id-Sj-isomer. ... 

Straight-chain alkanes, alkenes, and branched-chain alkenes (squalene) are detected in the hydrocarbon fraction. The squalene content is 120 mg/100 g. 

Alkenes can be hydroformylated " by treatment with carbon monoxide and hydrogen over a catalyst. The most common catalysts are cobalt carbonyls (see below for a description of the mechanism) and rhodium complexes, " but other transition metal compounds have also been used. Cobalt catalysts are less active than the rhodium type, and catalysts of other metals are generally less active. " Commercially, this is called the 0x0 process, but it can be carried out in the laboratory in an ordinary hydrogenation apparatus. The order of reactivity is straight-chain terminal alkenes > straight-chain internal alkenes > branched-chain alkenes. With terminal alkenes, for example, the aldehyde unit is formed on both the primary and secondary carbon, but proper choice of catalyst and additive leads to selectivity for the secondary product " or primary... 

Naming branched-chain alkenes When naming branched-chain alkenes, follow the lUPAC rules for naming branched-chain alkanes—with two differences. First, in alkenes the parent chain is always the longest chain that contains the double bond, whether it is the longest chain of carbon atoms or not. Second, the position of the double bond, not the branches, determines how the chain is numbered. Note that there are two 4-carbon chains in the molecule shown below, but only the one with the double bond is used as a basis for naming. This branched-chain alkene is 2-methylbutene. 

You are given a branched-chain alkene that contains one double bond and two alkyl groups. Follow the lUPAC rules to name the organic compound. 

These organo-zirconium derivatives give good acylations with simple acid chlorides25 (and even better yields if treated with A1C13). Thus any linear hexene gives 2-octanone 75 by zirconation and acetylation, and even branched chain alkenes such as 76 are acylated at the terminus 78 by this method. 

Note that there are two 4-carbon chains in the molecule shown in Figure 21.13a, but only the one with the double bond is used as a basis for naming. This branched-chain alkene is 2-methylbutene. 

The branched-chain alkenes (42), prepared by standard methods, on reduction and partial hydrolysis afforded the diol (43), which was cleaved with periodate and cyclized to give the bicyclic derivative (44), This is a possible synthetic precursor of brefeldin A. The cyano-derivative (45), which is stereochemically related to the prostaglandins, was then synthesized by use of the epoxide (46). ... 

Name the branched chain alkene or alkyne similar to alkanes. 

Naming branched-cKain alkenes The parent chain in an alkene is always the longest chain that contains the double bond, even if this is not the longest chain of carbon atoms. The numbering of the parent chain is determined by the position of the double bond. If there is more than one double bond, the positions of the double bonds are numbered so as to give the lowest set of numbers. The following example problem demonstrates how to name a branched-chain alkene. 

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