Naming Cycloalkanes If ambiguity exists,number H3C、6 1CH2CH3 carbon atoms so that third or fourth substituent has lowest -CH3 number possible. 3 1-Ethyl-2,6-dimethylcycloheptane H3C、4 2CH2CH3 Higher NOT CH3 6 H3C. CH2CH3 2-Ethyl-1,4-dimethylcycloheptane CH3 Lower Lower 6 5 3-Ethyl-1,4-dimethylcycloheptane Higher LmingAl Pigh Reerd
Naming Cycloalkanes ▪ If ambiguity exists, number carbon atoms so that third or fourth substituent has lowest number possible
Naming Cycloalkanes When two or more substituents could potentially receive the same numbers,number by alphabetical priority: CH3 CH3 1 CH2CH3 CH2CH3 3 5 2 NOT 3 1-Ethyl-2-methylcyclopentane 2-Ethyl-1-methylcyclopentane
▪ When two or more substituents could potentially receive the same numbers, number by alphabetical priority: Naming Cycloalkanes
Naming Cycloalkanes If halogens are present,treat them just like alkyl groups: CH3 CH3 2 NOT Br Br 1-Bromo-2-methylcyclobutane 2-Bromo-1-methylcyclobutane Additional examples: C B CH3 CH3 6 CHCH2CH3 5 CH3CH2 CH3 CH2CH3 1-Bromo-3-ethyl-5-methyl- (1-Methylpropyl)cyclobutane 1-Chloro-3-ethyl-2-methyl- cyclohexane or sec-butylcyclobutane cyclopentane Cangge Leaming All Pighs Resorved
▪ If halogens are present, treat them just like alkyl groups: ▪ Additional examples: Naming Cycloalkanes
4-2 Cis-Trans Isomerism in Cycloalkanes Cycloalkanes vs.Open-chain Alkanes Similarities -nonpolar;fairly inert Differences-cycloalkanes are less flexible than open- chain alkanes Rotation occurs around the carbon-carbon bond in ethane No rotation is possible around the carbon-carbon bonds in cyclopropane without breaking open the ring Larger cycloalkanes have increasing rotational freedom (a) Rotate
Cycloalkanes vs. Open-chain Alkanes ▪ Similarities – nonpolar; fairly inert ▪ Differences – cycloalkanes are less flexible than openchain alkanes ▪ Rotation occurs around the carbon-carbon bond in ethane ▪ No rotation is possible around the carbon-carbon bonds in cyclopropane without breaking open the ring ▪ Larger cycloalkanes have increasing rotational freedom 4-2 Cis-Trans Isomerism in Cycloalkanes
Cis-Trans Isomerism in Cycloalkanes Cycloalkanes:Two faces (as viewed edge on) Top face Bottom face Isomerism possible in substituted cycloalkanes cis-1,2-Dimethylcyclopropane trans-1,2-Dimethylcyclopropane
▪ Cycloalkanes: Two faces (as viewed edge on) Top face Bottom face ▪ Isomerism possible in substituted cycloalkanes Cis-Trans Isomerism in Cycloalkanes