Chapter 4 - Cycloalkanes - Chapter 4: Cycloalkanes Cyclic...

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Chapter 4: Cycloalkanes Cyclic alkanes or carbocycles or cycloalkanes are hydrocarbons containing single-bonded carbon atoms arranged in rings 4.1 Names and Physical Properties of Cycloalkanes The names of the cycloalkanes follow IUPAC rules o C n H 2n o Alkane names are preceded by prefix cyclo - o Only number carbons if there are more than one substituent attached to ring; carbon of attachment is defined as carbon 1 o For more than one substituent attached rings, lowest possible numbering sequence; if two sequences are possible, then alphabetical order of substituent names takes precedence o Radicals derived from cycloalkanes by abstraction of hydrogen atom are cycloalkyl radicals o Smaller units are treated as substituents to larger ones Disubstituted cycloalkanes can be stereoisomers o If the two substituents are on same side of ring, they are called cis o If the two substituents are on opposite sides of ring, they are called trans o Depicted by dashed-wedged line structures o Cis and trans are stereoisomers which are compounds that have identical connectivity but differ in spatial arrangement o Constitutional and structural isomers differ in connectivity o Conformations are stereoisomers but conformers are equilibrated by rotation whereas cis and trans isomers require breaking of bond The properties of the cycloalkanes differ from those of their straight-chain analogs o Cycloalkanes have higher boiling and melting points and densities than straight chain alkanes because of increased London interactions of more rigid and symmetric systems o Lower cycloalkanes of odd numbers have significantly lower melting points than lower cycloalkanes of even numbers because of differences in crystal packing forces 4.2 Ring Strain and the Structure of Cycloalkanes
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Chapter 4 - Cycloalkanes - Chapter 4: Cycloalkanes Cyclic...

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