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I know how to name alcohols, I just don't know what I should chose as the parent chain. Should I chose the cycle or the chain with the hydroxyl group. Here is an example:

enter image description here

My current algorithm tells me that this is 1-(propan-2-olyl)cyclohexane, because it always chooses the cycle with the most skeletal atoms for a parent chain no matter what else is present.

So my questions are:

  • In what situation an acyclic chain is chosen for a parent chain over a ring?
  • If this is one of those situations would the choice be affected if we add on hydroxyl group to both the ring and the chain?
  • If this is not one of those situations would the choice be affected if we increase the length of the acyclic chain and/or add more hydroxyl groups?
  • Something on a slightly different topic: is 1-(propan-2-olyl)cyclohexane a correct name or should it be 1-(propan-2-ol-1-yl)cyclohexane? I am not sure if the 1 is omitted or not.

P.S. Is there a place where I can find the Blue Book for free? I only have the 2004 draft and I am not sure how much of it is changed in the 2013 version?

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The compound given in the question contains a characteristic group $(\ce{-OH})$. Since there is only one characteristic group, the seniority order of classes is not relevant in this case; thus, the $\ce{-OH}$ substituent corresponds to the principal characteristic group that is expressed as a suffix (‘ol’).

According to the current version of Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013 (Blue Book), the senior parent structure has the maximum number of substituents corresponding to the principal characteristic group.

P-44.1 SENIORITY ORDER FOR PARENT STRUCTURES

When there is a choice, the senior parent structure is chosen by applying the following criteria, in order, until a decision is reached. These criteria must always be applied before those applicable to rings and ring systems (see P-44.2) and to chains (see P-44.3). Then criteria applicable to both chains and rings or ring systems given in P-44.4 are considered.

P-44.1.1 The senior parent structure has the maximum number of substituents corresponding to the principal characteristic group (suffix) or senior parent hydride in accord with the seniority of classes (P-41) and the seniority of suffixes (P-43).

(…)

Therefore, the correct name for the compound given in the question is ‘1-cyclohexylpropan-2-ol’ (not: ‘(2-hydroxypropyl)cyclohexane’). (Note that in ‘(2-hydroxypropyl)cyclohexane’, the locant ‘1’ of ‘1-(2-hydroxypropyl)cyclohexane’ is omitted since, according to Subsection P-14.3.4.2, the locant ‘1’ is omitted in monosubstituted homogeneous monocyclic rings.)

1-cyclohexylpropan-2-ol

If there is still a choice (for example, if the ring and the chain each have a substituent corresponding to the principal characteristic group), the ring or the chain can be the senior parent structure; however, for the preferred IUPAC name, the ring is always selected as the senior parent structure.

P-44.1.2.2 Systems composed of rings and chains (exclusive of linear phanes)

Two methods are recognized to name systems composed of rings and chains (exclusive of linear phanes).

(1) Within the same class, a ring or ring system has seniority over a chain. When a ring and a chain contain the same senior element, the ring is chosen as parent. Rings and chains are chosen regardless of their degree of hydrogenation. As a consequence, this approach prefers the choice of a ring over a chain in systems composed of cyclic and acyclic hydrocarbons.

(2) The context may favor the ring or the chain, so that, for example, substituents may be treated alike or an unsaturated acyclic structure may be recognized, or the one chosen has the greater number of skeletal atoms in the ring or in the principal chain of the acyclic structure.

(…) For selection of a preferred IUPAC name, see P-52.2.8.

 

P-52.2.8 Selection between a ring and a chain as parent hydride

Within the same heteroatom class and for the same number of characteristic groups cited as the principal characteristic group, a ring is always selected as the parent hydride to construct a preferred IUPAC name. In general nomenclature, a ring or a chain can be the parent hydride (see P-44.1.2.2).

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  • $\begingroup$ Is the characteristic group always cited as a prefix and not a suffix if it is in a substituent and if so, does that mean that it has the same priority for low locants as everything else? $\endgroup$ – K.Smith Apr 10 '16 at 20:01
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    $\begingroup$ @K.Smith Yes. In names of simple substituent groups, the presence of a free valence formally derived from the loss of one hydrogen atom from a parent hydride is denoted by the suffix ‘yl’. Since only one suffix can be placed at the end of a name, any further characteristic group of the substituent group is cited as prefix. $\endgroup$ – Loong Apr 10 '16 at 20:42
  • $\begingroup$ I see. I thought "yl" was an infix. $\endgroup$ – K.Smith Apr 10 '16 at 21:06

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