Final answer:
To classify alkenes in vitamin D3, use the IUPAC naming system, considering the longest carbon chain with the double bond as the parent chain and the placement and number of substituents on the double bond.
Step-by-step explanation:
To classify each alkene in vitamin D3 by the number of carbon substituents bonded to the double bond, you first need to understand the IUPAC naming system for alkenes. An alkene is named based on the alkane with the same number of carbon atoms, but with the suffix -ene to denote the double bond presence. When naming alkenes, the longest carbon chain containing the double bond is the parent chain, and the position of the double bond is specified by the lowest numbered carbon in the chain that is part of the double bond.
For example, the compound CH2=CHCH3 is named propene, as it contains a double bond in a three-carbon parent chain. If the alkene has substituents, they are named and numbered in a way that gives the double bond the lowest possible number. For instance, CH3CH2CH=CH2 is named 1-butene, and if there were a methyl group on the second carbon, it would be called 3-methyl-1-butene.
Applying this to vitamin D3, you would explain the alkenes based on their substitution. For instance, a tetrasubstituted alkene in vitamin D3 has four alkyl groups attached to its double-bonded carbons, while a trisubstituted alkene has three, and so on.