H-2, Names for Isotopically Modified Compounds

Continued from H-1, Symbols, Definitions and Formulae

CONTENTS

• H-2. NAMES FOR ISOTOPICALLY MODIFIED COMPOUNDS
  • Rule H-2.1. Isotopically substituted compounds
  • Rule H-2.2. Specifically labeled compounds
  • Rule H-2.3. Selectively labeled compounds
  • Rule H-2.4. Nonselectively labeled compounds
  • Rule H-2.5. Isotopically deficient compounds
  • Rule H-2.6. General and uniform labeling
  • Rule H-2.7. Exceptional changes in the hrefs of some unsymmetrically modified compounds
  • Rule H-2.8. Order of nuclide symbols
  • Rule H-2.9. Stereoisomeric isotopically modified compounds

• References for this section

Rule H-2.1. Isotopically substituted compounds (cf. Rule H-1.23)

2.11 - The name of an isotopically substituted compound is formed by inserting in parentheses (curves) the nuclide symbol(s), preceded by any necessary locant(s) (letters and/or numerals), before the name or preferably before the denomination of that part of the compound that is isotopically substituted. Immediately after the parentheses there is neither space nor hyphen, except that when the name, or a part of the name, includes a preceding locant, a hyphen is inserted.

Note:

In general, in organic nomenclature locants for suffixes, unsaturation, free valences, etc., cited ahead of the parent are considered as part of the name. In this report the practice of citing the isotopic descriptor ahead of such locants is followed; in biochemical usage the isotopic descriptor is often cited after such locants.

When polysubstitution is possible, the number of atoms substituted is always specified as a right subscript to the atomic symbol(s), even in case of monosubstitution.

Examples:

1.	14CH4	(14C)Methane
2.	CH32H	(2H1)Methane
3.	C2H2Cl2	Dichloro(2H2)methane
4.		1-[Amino(14C)methyl]cyclopentanol
5.		1-(Aminomethyl)cyclopentan(18O)ol or 1-(Aminomethyl)(18O)cyclopentanol
6.		2-Cyclohexen-1-(2H2)amine or (N,N-2H2)-2-Cyclohexen-1-amine
7.		N-[7-(131I)Iodofluoren-2-yl]acetamide
8.		Sodium ethyl (2,3-14C2)succinate

Rule H-2.2. Specifically labeled compounds (cf. Rule H-1.25)

2.21 - The name of a specifically labeled compound is formed by inserting in square brackets the nuclide symbol(s), preceded by any necessary locant(s) (letters and/or numerals), before the name or preferably before the denomination of that part of the compound that is isotopically modified. Immediately after the brackets there is neither space nor hyphen, except that when the name, or a part of the name, requires a preceding locant, a hyphen is inserted.

Note:

In general, in organic nomenclature locants for suffixes, unsaturation, free valences, etc., cited ahead of the parent are considered as part of the name. In this report the practice of citing the isotopic descriptor ahead of such locants is followed; in biochemical usage the isotopic descriptor is often cited after such locants.

When polylabeling is possible, the number of atoms that have been labeled is always specified as a subscript to the atomic symbol(s), even in the case of monolabeling. This is necessary in order to distinguish between a specifically and a selectively or nonselectively labeled compound.

The name of a specifically labeled compound differs from the name of the corresponding isotopically substituted compound (see Rule H-2.11) only in the use of square brackets surrounding the nuclide descriptor rather than parentheses (curves).

Examples:

1.	[14C]H4	[14C]Methane
2.	CH3[2H]	[2H1]Methane
3.		3-Methyl[1,1-2H2]-1-pentene *
4.		[5-2H1]-5H-Dibenzo[a,d]cycloheptene *
5.		4-([3-14C]-2-Thienyl)pyridine *
6.	C[2H2]Cl2	Dichloro[2H2]methane
7.	CH3-CH2-O[2H]	Ethan[2H]ol or [O-2H]Ethanol
8.		6-Methyl[2,2,3-2H3]-1,2,3,4-tetrahydro-l-naphthol **
9.		1-(Amino[14C]methyl)cyclopentanol
10.		[2,2-2H2]-1(2H)-Naphthalenone
11.		N-(7-[131I]Iodofluoren-2-yl)acetamide
12.		N-(6,7-[6-131I]Diiodofluoren-2-yl)acetamide

* Note that here the locant is part of the parent hydrocarbon or radical name.

** In cases such as this, treatment of hydro prefixes as nondetachable is preferred; see Rule C-l6.1l (ref. 6).

2.22 - In a name consisting of two or more words, the isotopic designator may be placed before the appropriate word or part of the word that includes the labeled nuclide(s), unless unambiguous locants are available or are unnecessary. (The same rule applies to isotopically substituted compounds (see Rule H-2.11)

Examples:

1.	CH2[2H]-CO2H	[2-2H1]Acetic acid
2.	CH3-CO2[2H]	[O-2H]Acetic acid or Acetic [2H]acid
3.	CH3-CH2-CH2-CH2-[14C]O2[2H]	[1-14C]Pentan[2H]oic acid or [1-14C,O-2H]Pentanoic acid
4.		Cyclohexane[2H]carboxylic acid or [O-2H]Cyclohexanecarboxylic acid
5.		4-([2-14C]Ethyl)benzoic acid
6.	H-[14C]O2Na	Sodium [14C]formate
7.	CH3-CH2-CO2[14C]H2-CH3	[1-14C]Ethyl propionate
8.	CH3-[14C]H2-CO2-CH2-CH3	Ethyl [2-14C]propionate
9.	[C6H5N2]+[35Cl]-	Benzenediazonium [35Cl]chloride

2.23 - In a trivial or semisystematic name consisting of one word, the isotopic designator may be placed before the full trivial name or inserted into the trivial name.

Examples:

Note: The alternative system based on the Boughton principles (see Introduction) denotes isotopic modification by citing the appropriate symbol and mass number (with subscripts and locants if necessary) following the portion of the name to which the symbol refers.

Example:

2-(Chloro-35Cl)-3-(methyl-d3)-pentane-1-d

According to the rules recommended here, the name for this compound is: 2-(³⁵Cl)chloro-3-[(²H₃)methyl] (1-²H₁)pentane.

Rule H-2.3. Selectively labeled compounds (cf. Rules H-1.26 and H-1.27)

2.31 - The name of a selectively labeled compound is formed in the same way as the name of a specifically labeled compound (see Rule H-2.21), except that the multiplying subscripts following the atomic symbols are generally omitted except as described by Rule H-2.32. Identical locants corresponding to the same element are not repeated.

The name of a selectively labeled compound differs from the name of the corresponding isotopically substituted compound in the use of square brackets surrounding the nuclide descriptor rather than parentheses (curves) and in the omission of repeated identical locants and multiplying subscripts.

Examples:

	Mixture of isotopically substituted compounds	when added to	is named
1.	CH32H, CH22H2, CH2H3, C2H4	CH4	[2H]Methane not [2H4]Methane
2.	CH3-CH2H-OH CH3-C2H2-OH	CH3-CH2-OH	[1-2H]Ethanol not [1,1-2H2]Ethanol
3.			[4-3H]Cyclohexanol not [4,4-3H2]Cyclohexanol
4.	14CH3-CH2-CO2-CH2-CH3 CH3-CH2-CO2-14CH2-CH3	CH3-CH2-CO2-CH2-CH3	1-14C]Ethyl [3-14C]propionate

2.32 - In a selectively labeled compound formally arising from mixing several known isotopically substituted compounds with the analogous isotopically unmodified compound, the number or the possible number of labeling nuclide(s) for each position may be indicated by subscripts to the atomic symbol(s) as described in Rule H-1.27

Examples

Rule H-2.4. Nonselectively labeled compounds (cf. Rule H-1.28)

2.41 - The name of a nonselectively labeled compound is formed in the same way as the name of a selectively labeled compound (see Rule H-2.31) but contains neither locants nor subscripts in the nuclide descriptor.

Examples:

Chloro[³H]benzene

[¹⁴C]Glycerol

Rule H-2.5. Isotopically deficient compounds (cf. Rule H-1.29)

2.51 - The name of an isotopically deficient compound may be formed by adding the italiziced syllable def immediately preceding, without a hyphen, the appropriate nuclide symbol, both enclosed in square brackets and cited before the name or that part of the name that is isotopically modified.

Example:

[def¹³C]Chloroform

Rule H-2.6. General and uniform labeling

2.61 - In the name of a selectively labeled compound in which all positions of the designated element are labeled, but not necessarily in the same isotopic ratio, the symbol "G" may be used in place of locants to indicate a "general" labeling.

Examples:

2.62 - In the name of a selectively labeled compound in which all positions of the designated element are labeled in the same isotopic ratio, the symbol "U" may be used in place of locants to denote "uniform" labeling.

Examples:

Note:

In the case of radioactive nuclides, "same isotopic ratio" means "same specific radioactivity".

2.63 - In the name of a selectively labeled compound, the symbol "U" (see Rule H-2.62) followed by appropriate locants, may similarly be used to indicate labeling in the same isotopic ratio at the specified positions.

Example:

D-Glucose in which ¹⁴C is equally distributed among positions 1, 3, and 5 may be designated as D-[U-1,3,5-¹⁴C]glucose.

Rule H-2.7. Exceptional changes in the names of some unsymmetrically modified compounds

2.71 - The name of an isotopically modified compound, substituted or labeled, may differ from the name of the unmodified analog when its structure includes identical units that are not identically modified in equivalent positions. Where there is ambiguity, such different groups must be expressed separately.

Example:

Unmodified compound:	Modified compound:
2,3-Diethyl-1-hexanol	2-([2,2-2H2]Ethyl)-3-ethyl-1-hexanol

Rule H-2.8. Order of nuclide symbols

2.81 - When isotopes of different elements are present as nuclides in an isotopically modified compound, their symbols are arranged in alphabetical order if they are inserted at the same place in the name.

Examples:

Note:

For numbering priority between N and N', see Rule H-3.21.

2.82 - When several isotopes of the same element are present as nuclides in an isotopically modified compound, their symbols are arranged in the order of increasing atomic mass number if they are inserted at the same place in the name.

Examples:

Rule H-2.9. Stereoisomeric isotopically modified compounds

2.91 - Two types of stereoisomeric isotopically modified compounds are possible: (a) those in which the stereoisomerism results from isotopic modification, and (b) those whose analogous unmodified compounds are stereoisomers.

The nomenclature of stereoisomers of isotopically modified compounds follows the general methods of stereochemical nomenclature as described in Section E (ref. 6).

Stereochemical affixes are cited at the specified place in the name according to the stereochemical rules. When they must be inserted into the name at the same place as isotopic descriptors, the stereochemical affixes are cited first.

Examples in which stereoisomerism results from isotopic modification:
1.		(S)-(1-2H1)Ethanol
2.		(S)-[1-2H1]Ethanol
3.		(S)-[2-2H1]-1-Propanol
4.		(2R,3S)-2-Chloro[3-2H1]-2-butanol
5.		(E)-[1-2H1]Propene
Examples of isotopically modified stereoisomers:
6.		(E)-1-Chloro[2-2H]-2-butene
7.		(S)-[2-2H]-2-Butanol
8.		(R)-3-Methyl[3-2H]-2-butanol
9.		(R)-sec-Butyl (2-14C)acetate
10.		[14C]Methyl (R)-2-methylbutyrate or (R)-([14C]Methyl 2-methylbutyrate)
11.		(Z)-[1,1,4,4-2H4]-2-Butene-1,4-diol

2.92 - Stereochemical affixes (for example D and L) added according to the rules of special classes,such as carbohydrates, amino acids, steroids, etc., usually refer to the parent substance (or unmodified compound) according to the particular class of compounds. However, isotopic descriptors follow the stereochemical descriptors in these classes, according to biochemical usage.

Note:

In general, in organic nomenclature locants for suffixes, unsaturation, free valences, etc., cited ahead of the parent are considered as part of the name. In this report the practice of citing the isotopic descriptor ahead of such locants is followed; in biochemical usage the isotopic descriptor is often cited after such locants.

Examples:

l.	L-[3,4-13C,35S]Methionine
2.	L-[3-14C,2,3-2H2,15N]Serine
3.	5-[17-2H]Pregnane
4.	(24R)-5-[24-2H1]Cholestane
5.	2-([18F]Fluoro)-2-deoxy-D-glucose

References

4. "The Naming and Indexing of Chemical Substances for Chemical Abstracts During the Ninth Collective Period (1972-1976)", para 220, p. 111I, a reprint of Section IV of the Introduction to the Chemical Abstracts Volume 76 Index Guide.

6. I.U.P.A.C. Nomenclature of Organic Chemistry, Sections A, B, C, D, E, F and H (1979 edition), Pergamon Press, Oxford. 1979.

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