Chapter 10 Introduction to Organic Chemistry: Alkanes 10.3 Alkanes with Substituents
Isomers of Butane Isomers • have the same molecular formula. • have different atom arrangements. • of butane (C4H10) are a straight chain and a branched chain.
Alkyl groups Alkyl groups are • alkanes that are missing one H. • substituents attached to carbon chains. • named with a –yl ending. H H C CH3 methyl H H H H C C CH3 CH2 ethyl H H
Naming Substituents In the IUPAC system, • a carbon branch is named as an alkyl group. • halogen atoms are named as halo. TABLE 10.6
Alkanes with Substituents CH3 CH3 CH CH3 methylpropane methyl groups CH3 CH3 CH3 CH CH2 CH CH3 2,4-dimethylpentane
Naming Alkanes Give the name of CH3 CH3 CH3─CH─CH─CH3 STEP 1 Name the longest continuous chain. CH3 CH3 CH3─CH─CH─CH3 butane
Naming Alkanes Give the name of CH3 CH3 CH3─CH─CH─CH3 STEP 2 Number chain from end nearest substituent . CH3 CH3 CH3─CH─CH─CH3 1 2 3 4 STEP 3 Locate substituents and name alphabetically. 2,3-dimethylbutane Note: when more substituents present on same carbon atom, its gets priority
Learning Check Write the name of ClCH3 CH3─CH2─CH─CH─CH3
Solution STEP 1 Longest chain is pentane. STEP 2 Number chain from end nearest substituent. ClCH3 CH3─CH2─CH─CH─CH3 5 4 3 2 1 STEP 3 Locate substituents and name alphabetically. 3-chloro-2-methylpentane
Learning Check Give the IUPAC name for each of the following: A. CH3CH3 | | CH3─CH─CH2 ─CH─CH3 B. ClCH3 || CH3─CH2─CH─CH2─C─CH2─CH3 | Cl
Solution A. CH3CH3 | | CH3─CH─CH2 ─CH─CH3 2,4-dimethylpentane 1 2 3 4 5 B. ClCH3 more substituents = C3 || CH3─CH2─CH─CH2─C─CH2─CH3 | Cl 7 6 5 4 3 2 1 3,5-dichloro-3-methylheptane
Learning Check Draw the condensed structural formula for 2-bromo-4-chlorobutane.
Solution 2-bromo-4-chlorobutane STEP 1Longest chain has 4 carbon atoms. C─C─C─C STEP 2 Number chain and add substituents. Br C ─ C ─ C ─ C ─ Cl 1 2 3 4 STEP 3 Add hydrogen to complete 4 bonds to each C. Br CH3─CH─CH2─CH2─Cl
Naming Cycloalkanes with Substituents The name of a substituent is placed in front of the cycloalkane name. methylcyclobutane CH3 chlorocyclopentane Cl
Learning Check Name each of the following. 1. CH3 CH2─CH3 2.
Solution Name each of the following. 1. methylcyclopropane 2. ethylcyclohexane