Nomenclature Problems: Name to Structure

In these problems you will be asked to draw the structures corresponding to compound names.

Tens of millions of organic compounds have already been studied, and the number of possible structures is infinite, so a very sophisticated system is needed for naming them. The most widely used system is that formulated by the International Union for Pure and Applied Chemistry, usually called the IUPAC system. Although software is increasingly used for chemical nomenclature, it is still important that chemists be able to understand IUPAC names.

Prequisite learning:

Functional groups
Basics of organic nomenclature

Learning Objectives:

Draw the structures of moderately complex organic molecules from the IUPAC names.
Demonstrate an understanding of the principles of organic nomenclature.

Free Learning Resources

OrgChem101 (Flynn, Ottowa) Organic Nomenclature

Introductory IUPAC Organic Nomenclature (Hunt, Calgary)

Organic Chemistry With a Biological Emphasis (Soderberg) Functional groups and organic nomenclature

Problem settings

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Select one or more families of compounds by clicking the checkboxes below.

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Problems

Select the compound type(s) and the initial problem difficulty level from the options on the left, and then click the "Get Problem" button.

When the problem is displayed, further instructions will be provided here.

Guide to drawing structures in the molecular editor

JSME: Bruno Bienfait and Peter Ertl, JSME: a free molecule editor in JavaScript, Journal of Cheminformatics 5:24 (2013).

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JSmol 3D structure viewer (Help)

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How to Solve Name to Structure Problems

Deducing the structure of a compound from its name is relatively straightforward when you are familiar with the basics of organic chemistry nomenclature. A detailed guide to the procedure is available as a pdf, and an outline is provided below. When you try the problems above, your answer will be analysed by checking that you have performed each the steps shown below, and the feedback will be structured accordingly. (Note that deducing the IUPAC name for an organic compound from its structure is a more difficult task and requires a somewhat different procedure.)

Step	Procedure	Notes
1	Draw the parent chain or ring.	Look for the name of the parent chain or ring (cyclo prefix) towards the end of the compound name. It will indicate the number of carbons in the chain or ring. If the parent is a chain, number the carbons from one end to the other. If it is a ring, number the carbons from an arbitrary starting point. However, if it is bicyclic or there are heteroatoms in the ring, there may be a specific numbering scheme (see the detailed guide).
2	Add the principal functional group(s) to the parent.	The suffix at the very end of the name will indicate if one or more 'principal functional groups' are present. For example, a name ending in '-one' means that the structure contains a ketone (C–C(=O)–C) group and its position on a chain will be specified by a 'locant', e.g. pentan-2-one is CH₃–C(=O)–CH₂–CH₂–CH₃. See the detailed guide for a Table showing the suffixes for common functional groups.
3	Add CC double and/or CC triple bondsCC double and/or CC triple bonds to the parent.	If CC double and/or CC triple bonds are present in the parent chain or ring, its name will end in '-en(e)' or '-yn(e)', or a combination of these, possibly with 'multiplicative prefixes' (di, tri, etc.), rather than in '-an(e)'. A 'locant' will indicate the first carbon of each unsaturated bond. For example, hepta-1,3-diene-6-yne is a seven-carbon chain with a double bond between carbons 1 and 2, a double bond between carbons 3 and 4, and a triple bond between carbons 6 and 7 (CH₂=CH–CH=CH–CH₂–C≡CH).
4	Add substituents to the parent and/or the principal functional group.	'Substituents' are groups that are attached to the parent chain or ring, replacing hydrogens on the parent. A list of the substituents (if any) is found as a list of prefixes before the parent name. In most cases, each substituent prefix will be accomapnied by a 'locant' that gives its position on the parent, or on the principal functional group. For example, 2-methylhexane indicates a one-carbon substituent (methyl) on the 2^nd carbon of a six-carbon chain, and N-ethylpropanamide indicates a two-carbon substituent (ethyl) on the N of propanamide, i.e. CH₃–CH₂–C(=O)–NH–CH₂–CH₃. Common substituents include alkyl and cycloalkyl groups (e.g. methyl-, cyclopropyl-), alkyloxy groups (e.g. methoxy-, hexyloxy-), halogen atoms (fluoro-, chloro-, etc.), and nitro- (O₂N-). However many functional groups, e.g. hydroxy- (HO-), and rings, e.g. phenyl (C₆H₅-), can be present as substituents; see the detailed guide for Tables of substituent prefixes.
5	Draw the stereochemistry at chirality centres and/or alkenes.	Chirality centres can have two possible configurations, which are specified as R or S according to the Cahn-Ingold-Prelog (CIP) rules. Alkenes that can have two configurations are specified as E or Z according to the CIP rules. The final step in drawing the structure is to check if any of these 'stereochemical descriptors' are shown at the start of the name and to draw the appropriate stereochemistry. If there is more than one stereochemical descriptor of the same type (R/S or E/Z), each will have a 'locant'. See here for an excellent descripion of the application of the CIP rules to chirality centres and alkenes.