# What should be the name of this substituted cyclopentane?

I think its name is 5-amino-3-bromo-4-chloro-2-hydroxycyclopentan-1-carbonitrile. Is that correct?

• What should I do wait please sir .. Feb 17 '16 at 18:48
• @_Pi5 what do YOU see in your browser? Try uploading again, after checking your picture locally. If this should be a problem instead of simply a wrong click, try uploading a test image (labeled so, to avoid confusion and undeserved down-votes). Feb 17 '16 at 19:26
• Yea, now I can see something! Feb 17 '16 at 19:36
• Note your NH2 is the wrong way round, I've edited it Feb 18 '16 at 21:05

According to the current version of Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013 (Blue Book), the preferred suffix for the principal characteristic group $\ce{{}-CN}$ is ‘carbonitrile’. Therefore, the name of the parent structure of the compound given in the question is ‘cyclopentane-1-carbonitrile’ (note that the locant ‘1’ would be omitted in monosubstituted homogeneous monocyclic rings, i.e. ‘cyclopentanecarbonitrile’).

The relevant rules for the numbering of locants for the four substituent prefixes (‘amino’, ‘bromo’, ‘chloro’, and ‘hydroxy’) are:

P-14.3.5 Lowest set of locants

The lowest set of locants is defined as the set that, when compared term by term with other locant sets, each cited in order of increasing value, has the lowest term at the first point of difference; (…)

and

P-14.4 NUMBERING

When several structural features appear in cyclic and acyclic compounds, low locants are assigned to them in the following decreasing order of seniority:

(…)

(f) detachable alphabetized prefixes, all considered together in a series of increasing numerical order;

(g) lowest locants for the substituent cited first as a prefix in the name;

(…)

Note that Rule (f) takes precedence over Rule (g).

In accordance with Rule (f), the compound given in the question could be named as 2-amino-4-bromo-3-chloro-5-hydroxycyclopentane-1-carbonitrile as well as 5-amino-3-bromo-4-chloro-2-hydroxycyclopentane-1-carbonitrile since both names correspond to the locant set ‘2,3,4,5’. However, according to Rule (g), this example is named as 2-amino-4-bromo-3-chloro-5-hydroxycyclopentane-1-carbonitrile rather than 5-amino-3-bromo-4-chloro-2-hydroxycyclopentane-1-carbonitrile since ‘amino’ is cited first as a prefix in the name.

• Loong, do you lurk in the nomenclature question list, poised to slam down Blue Book quotes? Wow. Feb 17 '16 at 19:43
• @Brian Sure! Even if a question is not a duplicate, many nomenclature questions can be answered using parts copied from similar answers.
– user7951
Feb 17 '16 at 19:52
• So can we say that we are following the priority order of functional groups just while making the backbone af5er that we follow alphabetical order ??? Feb 18 '16 at 16:40
• @Pi5 You use the priority order to identify the characteristic group that is expressed as a suffix (here: carbonitrile) and that receives the lowest locant (here: 1). Then, low locants are given to the prefixes, all considered together (here: 2,3,4,5). If a choice still remains, the lowest locant (here: 2) is given to the substitutent cited first in the name (here: amino), which corresponds to alphabetical order.
– user7951
Feb 18 '16 at 17:00
• @Pi5 You can find examples for Rule (f) here and here, and for Rule (g) here, here, here, here, here, and here.
– user7951
Feb 18 '16 at 17:12