Copyright © Houghton Mifflin Company. All rights reserved. 14 | 1 Cycloalkanes Members of the cycloalkane group possess rings of carbon atoms in a ring or circular structure. They have the general formula C n H 2n. The smallest possible ring consists of cyclopropane, C 3 H 6. Section 14.3

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 2 The First Four Cycloalkanes Section 14.3

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 3 Is it the Parent or the Branch? When naming Cycloalkanes, you must determine if the ring is the “Parent” (main chain) or is it an attachment group. If the Cyclo ring has more carbons than any of the other alkyl groups attached, it is the parent. If the Cycloring has less carbons, then name it as a side group. (Cyclopropyl, Cyclobutyl…) Section 14.3

Cyclic Compounds – Parent? In this example, the ring has four carbons and the chain has eight. The chain is longer than the cyclo group, so the ring is a prefix. The ring is a cyclobutyl group on Carbon #1 1-cyclobutyloctane.

Parent vs Side Group In this example, the ring has five carbons and the alkyl group has three. The five-carbon ring is longer than the three carbon chain, so the ring is the parent and is called cyclopentane. The is an alkyl group will be on #1 (of course – that #1 isn’t even needed!)

Cyclic Compounds Word of caution: don’t double dip… its really easy to double count the carbon (*) Alkyl groups consist of only those Carbons BEYOND the ring carbons. Thus, this is a propyl group not a butyl group. Propylcyclopentane

Copyright © Houghton Mifflin Company. All rights reserved. 14 | 7 Draw: 1-chloro-2-ethylcyclopentane Section 14.3

When Multiple Groups are Attached When a ring has multiple groups, the rule for numbering is: “Number around the ring so as to arrive at the lowest possible sum of the position numbers”. The sum in this molecule is = 4.

Cyclic Compounds – Multiple Groups How about this one? 1,2,4-trimethylhexane

Cyclic Compounds – Multiple Groups If you have two possibilities for lowest possible sum, THEN (and only then) you should alphabetize to prioritize your groups. What about this one? 1-etyl-3-methylcyclopentane

Practice Problem Copyright © Houghton Mifflin Company. All rights reserved. 14 | 11 1)Draw the line structure for: 1-ethyl-3-iodocyclopentane 2) Draw the line structure for: 2-ethyl-1,1,3-trimethyl-cyclobutane

Name these molecule Copyright © Houghton Mifflin Company. All rights reserved. 14 | 12 3) Draw the line structure for: 4-cyclobutyl-3,5-difluoro-3-methyloctane