Carbon alkenes

Although ethylene is the only two carbon alkene and propene the only three carbon alkene there are four isomeric alkenes of molecular formula C4Hj ... 

Note that there is no one-carbon alkene corresponding to methane, since hydrogen can never form more than one covalent bond, and there is no other carbon atom in the structural formula. Therefore, the first compound in the alkene series is ethene, while the corresponding two-carbon compound in the alkane series, ethane, is the second compound in the series, with methane the first. 

An aikene is a hydrocarbon that contains a carbon-carbon double bond. Because they contain fewer hydrogens than alkanes with the same number of carbons, alkenes are said to be unsaturated. 

The three-carbon alkene, propylene, is also an important industrial compound. It is used in the production of the plastic polypropylene, which is used in molded parts, electrical insulation, and packaging. Propylene is also used in the production of a wide variety of chemicals. 

In the presence of 60% sulfuric acid, 2-methylpropene is not converted to a long-chain polymer, but to a mixture of eight-carbon alkenes. The mechanism is like that of the polymerization of 2-methylpropene under nearly anhydrous conditions, except that chain termination occurs after only one 2-methylpropene molecule has been added ... 

B is correct. The bonds are stabilized by resonance and are shorter and stronger than carbon-carbon alkane bonds but longer and weaker than carbon-carbon alkene bonds. 

Alkenes are hydrocarbons containing at least one double bond. For alkenes with only one double bond, the empirical formula is CnH2n. The names for all alkenes end with -ene. The naming system on alkenes is the same as alkanes, with the exception of the -ene ending. For example, the two-carbon alkane, C2H6, is called ethane, while the two-carbon alkene, C2H4, is called ethene. 

It is possible to synthesize the following aldehyde from an appropriate 5-carbon alkene by using an appropriate transition metal catalyst ... 

The rules for naming an unsaturated hydrocarbon with fewer than four carbon atoms are similar to those for naming alkanes. A two-carbon alkene is named ethene, with the suffix -ene indicating that the molecule is an alkene. A three-carbon alkyne is named propyne, with the suffix -yne indicating that the molecule is an alkyne. 

Unsaturated hydrocarbons that contain one or more double covalent bonds between carbon atoms in a chain are called alkenes. Because an alkene must have a double bond between carbon atoms, there is no 1-carbon alkene. The simplest alkene has two carbon atoms double-bonded to each other. The remaining four electrons— two from each carbon atom—are shared with four hydrogen atoms to give the molecule ethene (C2H4). 

Naming alkenes Alkenes are named in much the same way as alkanes. Their names are formed by changing the -ane ending of the corresponding alkane to -ene. An alkane with two carbons is named ethane, and an alkene with two carbons is named ethene. Likewise, a three-carbon alkene is named propene. Ethene and propene have older, common names ethylene and propylene, respectively. 

Although cyclopropylidenes have been generated by a number of independent methods which include cycloaddition of atomic carbon to alkenes, decarbonylation of cyclo-propylideneketenes, decarboxylation of oxaspiropentanes, from a preparative viewpoint, the a-elimination reaction of cyclopropane derivatives is most practical because of the mild reaction conditions and the availability of the starting materials. These methods are illustrated by the formation of allenes from atomic carbon/alkene reactions in Table 1 and in the preparation of 3/4, and from cyclopropanes in the preparation of 5/6. Examples showing allenes from decarbonylation of cyclopropylideneketenes are shown in the preparations of compounds 7/8, 9, 10, " and 11. ... 

Table 1. Allenes from Atomic Carbon/Alkene or Cyclopropane Reactions...

---