Nomenclature Changes for CA Index Names

Introduction

Effective the week of December 11, 2006, CAS began implementing a
number of changes that simplify CA index nomenclature and make CA index
names more logical, consistent, and easier to understand. These changes
represent the most significant group of modifications to CAS index
nomenclature since the introduction of 9th Collective Index (9CI)
nomenclature in 1972.
All existing names have been retained on the substance records and the newnames are being added during 2007.
The examples show both the new CA index names and the 9CI names forcomparison.

Summary of
Changes

The key nomenclature changes include:
General Changes
1. New Definition for Ketones
2. Elimination of Unexpressed Amides
3. Elimination of Aldehydo Substituents
4. Binuclear Nitrogen Radicals
5. Names for Sulfur, Selenium, and Tellurium Radicals Double Bonded to
Nitrogen6. New Ranking of Silane for Choice of Parent
7. Acylheteroatom Substances
8. Chalcogen-Substituted Borons
9. Non-traditional Alcohol Esters
10. Selecting the Preferred Tautomer
11. Ylide Elimination
12. Aci-Nitro Term
13. Abnormal Valent Heteroatom in Rings
14. Numerical Ratios for Multicomponent Substances
15. Multicomponent Substances Containing an Acid
16. Metal Salt Terms
17. Fewer Stereoparent NamesContinued on next page1

Amino Acid and Peptide Names
18. Order of Precedence
19. Heterodetic Homomeric Peptides
20. Unexpressed Amides of Peptides
21. S-Oxides
22. Peptide Stereoparents
Locant Rules
1.1 Geneva Suffixes
1.2 Conjunctive Suffixes
1.3 Other Functional Suffixes
2. Subtractive Suffixes
3. Free Valences
4 Substituent Prefixes
4.1 Multiplying Radicals
4.2 Other Substituent Prefixes
4.3 Prefixes with Greek and Capitalic Letter Locants
CA IndexNames

Effective with 2007, CAS no longer categorizes information by collective
index periods. The 15CI period covers 2002-2006. The CA index names in
CAS REGISTRYSM no longer have a “CI” label. The “CI” labels (6CI, 7CI,
8CI, 9CI) have been retained for those names that have them.

UpdatedRegistry

The CA index name for all substances in REGISTRY are being updated in2007 to comply with the new rules. New compounds will receive the new
CA index name. The previous CA index name, if different, will appear in the
OTHER CA INDEX NAMES portion of the REGISTRY display. No names
will be removed.

QuestionsIf you have questions concerning these changes, please contact CAS
Customer Care at help@cas.org or 800-753-4227.

Appendix IV of
the CA Index
Guide

The full details of the nomenclature changes previously published as
Appendix IV of the CA Index GuideSM will be published at a later time.

2

General Changes

1. New
Definition for
Ketones

Ketones are a class of compounds characterized by the presence of the groupX
where X is any chalcogen. This group may be attached to carbon or otherelements with the exception of hydrogen and those that could form an acid,acid derivative or amide name.
Organometallic and coordination compounds will continue to be named assuch.

(CH3)3Si

CO

CH2

CH3

New: 1-Propanone, 1-(trimethylsilyl)9CI: Silane, trimethyl(1-oxopropyl)2. Unexpressed
AmidesAmides in which the nitrogen atom of the amide group is part of aheterocyclic ring are not treated as unexpressed amides. These substances are
named at the highest ranking function present.

N

CO

CH2

CH3

New: 1-Propanone, 1-(1-piperidinyl)9CI: Piperidine, 1-(1-oxopropyl)O
N

New:
9CI:

N

Methanone, 1H-imidazol-1-yl-4-pyridinyl1H-Imidazole, 1-(4-pyridinylcarbonyl)-

3N3. Aldehydo
Substituents

Replacement of the aldehyde hydrogen is not permitted. Aldehyde names
will be restricted to carbonyl groups bonded to hydrogen or an isotope ofhydrogen.
Some exceptions to this rule are permitted in carbohydrate nomenclature.
H3C

CO

NO

New: Ethanone, 1-nitroso9CI: Acetaldehyde, 1-nitroso4. Binuclear
Nitrogen
Radicals

The names for the following binuclear nitrogen radicals are revised asfollows:
New
9CI
azi
3H-diaziridine (component ring in a spiro name)azino
1,2-hydrazinediylidene
azo
diazenyl or 1,2-diazenediyl
azoxy(1-oxidodiazenyl) or (2-oxidodiazenyl) or(1-oxido-1,2-diazenediyl)
hydrazi
diaziridine (component ring in a spiro name)hydrazino
hydrazinyl
hydrazo
1,2-hydrazinediyl
hydrazono
hydrazinylidene
Me

Me
N

N
N

N

N
N

Me

Me

New: Pyrimidine, 2,2'-(1,2-diazenediyl)bis[4,6-dimethyl9CI: Pyrimidine, 2,2'-azobis[4,6-dimethyl-

45. Sulfur,
Selenium, andTellurium
RadicalsGroups containing a sulfur, selenium, or tellurium atom attached by a doublebond to nitrogen are now named as substituents. The following new radical
names will be used:
S

Se

Te

Tetravalent

λ4-sulfanylidene

λ4-selanylidene

λ4-tellanylidene

Hexavalent

λ6-sulfanylidene

λ6-selanylidene

λ6-tellanylidene

Si(CH3)3
N
F3C

CO

N

S
N
Si(CH3)3

New: Acetamide, N-[bis[(trimethylsilyl)imino]-λ6-sulfanylidene]-2,2,2trifluoro9CI: Sulfur triamide, (trifluoroacetyl)bis(trimethylsilyl)6. New
Ranking of
SilaneSilanes are now ranked between cyclic carbon parents and acyclic carbon
parents. Silyl groups are used primarily as blocking groups and as such are
not the primary structural feature of interest.
O
Me

Si

Ph

New: Benzene, (methyloxosilyl)9CI: Silane, methyloxophenylMe2SiH

O

O

New: Benzene, 1,3-bis[(dimethylsilyl)oxy]9CI: Silane, [1,3-phenylenebis(oxy)]bis[dimethyl-

5

SiHMe2

7.
Acylheteroatom
Substances

Acylheteroatom substances are named at the highest function present. The
highest functional group is NOT overstepped to preserve the Acylheteroatom
grouping.
Et
Et

O

Ge

Me

Et

New: Ethanone, 1-(triethylgermyl)9CI: Germane, acetyltriethylO H
P

Et

New: 1-Propanone, 1-(diphenylphosphino)9CI: Phosphine, (1-oxopropyl)diphenyl8. Chalcogen
Substituted
Borons

Chalcogen-substituted borons are names as boron acids.
HO
B

H
N

H
N

HO

OH
B
OH

New: Boronic acid, B,B'-1,2-hydrazinediylbis9CI: Hydrazine, 1,2-diborono-

69. Nontraditional
Alcohol Esters

Non-traditional alcohol esters which are esterified with alcohols other than
the traditional ones of carbon and silicon are now named as esters.
Oximes of aldehydes and ketones are retained.
O

Me

C

N

S

NH2

Me

New: Carbamothioic acid, N,N-dimethyl-, S-azanyl ester
9CI: Thiohydroxylamine, S-[(dimethylamino)carbonyl]10. Preferred
Tautomer

Only structure-based rules are used for selecting the preferred tautomer. In
the 9CI system, a combination of nomenclature and structure-based rules
were used to select the preferred form of a tautomer to name. Existing names
for most tautomers are retained.
H
N

O

N

N

N
H

New: 6(5H)-Pteridinone, 7,8-dihydro9CI: 6(5H)-Pteridinone, 1,7-dihydro-

H
N

Ph

N

Me

C

CO2H

New: Acetic acid, 2-(methylimino)-2-(phenylamino)9CI: Acetic acid, (methylamino)(phenylimino)-711. Ylide
Elimination

Zwitterionic compounds in which the site of the cationic center is known are
generally named as inner salts. The term “ylide”, used in 9CI nomenclature,
is not used in the new CA index nomenclature.
O
N

N
H

O

New: Pyridinium, 1-(1,2,3,4-tetrahydro-2,4-dioxo-3-quinolinyl)inner salt
9CI: Pyridinium, 1,4-dihydro-2,4-dioxo-3(2H)-quinolinylide
CN
NC

C
O

New: Pyrylium, 3-(cyanomethylene)-2,3,4,5-tetrahydro-, inner salt
9CI: Pyrylium, 3-(cyanomethylene)-2,3,4,5-tetrahydro-, ylide
12. Aci-Nitro
Term

The term aci-nitro will not be retained by overstepping a higher functionality.
O
H3C

CH

N

O
O

CH2

CH2

New: Propanoic acid, 3-[(ethylideneoxidoamino)oxy]9CI: Ethane, [(2-carboxyethyl)-aci-nitro]-

8

C

OH

13. Abnormal
ValentHeteroatom in
Rings

The lambda system will be used for naming rings containing an abnormal
valent heteroatom.
S
C

N

C

N

New: 1λ,4δ−1,2,3-Thiadiazole
9CI: 1,2,3-Thia(SIV)diazole
14. Numerical
RatiosNumerical ratios are cited for multicomponent substances. The 9CI systemused a combination of numerical ratios and numerical prefixes
New: Glycine, N-(aminoiminomethyl)-N-methyl-, hydrate (1:1)
9CI: Glycine, N-(aminoiminomethyl)-N-methyl-, monohydrate

15.
Multicomponent
Acids

All multicomponent substances containing an acid are named as "ides" forhydrohalides and "ates" for other acids.
New: Benzenepropanoic acid, hydrochloride (1:1)
9CI: Benzenepropanoic acid, compd. with hydrochloric acid (1:1)

16. Metal Salt
Terms

Metal salt terms in uninverted names appear in the expected way.
16CI: polymer with sodium hydroxyacetate (1:1)
9CI: polymer with hydroxyacetic acid monosodium salt

9

17.
Stereoparent
Names

The number of stereoparent names has been reduced by eliminating nearly
3,000 obscure stereoparents that had to be recognized when naming andsearching. Common stereoparents such as insulin, cholane, morphinan,
glucose, etc. have been retained.
Me
Me
R

H
R

R

Me

S
S
H
H

Me
H

H

R

X

New: 1H-Indene, octahydro-7a-methyl-1-[(1R)-1-methylbutyl]-4-[2-[(2R)-2-methylcyclohexyl]ethyl]-, (1R,3aS,4S,7aR)9CI : 9,10-Secocholane

New: Cyclo(glycyl- L-valyl-L-leucyl-L-leucyl-L-tyrosyl-L-prolyl-L-leucyl)
9CI : Pohlianin A

10Amino Acid and Peptide Nomenclature

18. Order ofPrecedence

The order of precedence of standard amino acids now reads as follows:
glutamic acid > aspartic acid > tryptophan > histidine > proline >tyrosine > phenylalanine > lysine > norleucine > glutamine >arginine > ornithine > isoleucine > alloisoleucine > leucine >norvaline > asparagine > threonine > allothreonine > homoserine >methionine > homocysteine > valine > isovaline > serine >cystine > cysteine > alanine > β-alanine > glycine
The new rankings attach greater weight to side-chain functional groups.
Also, valine outranks the rare isovaline, and cystine is grouped with its
reduced form, cysteine, instead of being separated from it by serine.

19. Heterodetic
Homomeric
PeptidesIn most peptides, the amino acid residues are connected solely by amide
bonds. However, in a heterodetic homomeric peptide (HHP), at least one of
the bonds connecting the residues is an ester bond between the carbonylgroup of one amino acid and the oxygen or sulfur of a hydroxy or mercaptoamino acid. Prior to the new rules, HHPs were according to the position of
the hydroxy or mercapto amino acid in the structure.
The new rule is that regardless of the position of the hydroxy or mercaptoamino acid residue in the structure, an amino acid residue attached to thehydroxy or mercapto group will be named as an O or S substituent on that
residue.
New:
9CI:

L-Serine, N,O-bis[N-(1-oxododecyl)-L-α-glutamyl]L-Serine, N-(1-oxododecyl)-L-α-glutamyl-, 5-hydrogen N(1-oxododecyl)-L-glutamate (ester)

11

20.
Unexpressed
Amides of
PeptidesUnder the 9CI rule for naming unexpressed amides of peptides, an amino acidamide was the heading parent, and in the process of coming up with thatparent one or more residues had to be sacrificed. In some cases, all of themwere sacrificed if no acceptable amino acid amide parent were available.
Now all the residue names will be preserved as a peptidyl radical—a
substituent on the ring. Users are able to search for many sequences by namethat before could be searched only by substructure.
New:
9CI:

21. S-Oxides

Piperidine, 1-(L-methionyl-L-serylglycyl)L-Serinamide, L-methionyl-N-[2-oxo-2-(1-piperidinyl)ethyl]-

S-Oxides of sulfur-containing amino acids are named at the peptide.
O
S

CO2H

Me
NH2

New: D-Methionine, S-oxide
9CI: Butanoic acid, 2-amino-4-(methylsulfinyl)-, (2R)O
NH2 O
Et
S
CH2
New: S-ethyl-S-oxidocysteinyl9CI: 3-(ethylsulfinyl)alanyl-

12

CH

C

N

R

22. Peptide
Stereoparents

The number of peptide stereoparents has been reduced from about 3,000 to
fewer than 100 of the most studied peptides (as judged by the number ofderivatives at those index headings). The rest will be assigned sequencenames, cyclo names, and occasionally derivative names based on retained
stereoparents.
The new peptide stereoparents consist of the following:
Actinomycin D [50-76-0]
Alamethicin I [59588-86-2]
α-Amanitin [23109-05-9]
Angiotensin I [9041-90-1]
Angiotensin II [11128-99-7]
Angiotensinogen (tetradecapeptide renin substrate) [64315-16-8]
Apamin [24345-16-2]
Apamin (reduced) [28047-76-9]
Bombesin [31362-50-2]
Bradykinin [58-82-2]
Caerulein [17650-98-5]
Calcitonin (human) [21215-62-3]
Calcitonin (human reduced) [27686-18-6]
Calcitonin (salmon) [47931-85-1]
Calcitonin (salmon reduced) [25596-79-6]
α-Calcitonin gene-related peptide (human) [90954-53-3]
α-Calcitonin gene-related peptide (human reduced) [90877-18-2]
Charybdotoxin [95751-30-7]
Charybdotoxin (reduced) [115422-61-2]
α1-24-Corticotropin [16960-16-0]
α1-39-Corticotropin (swine) [9061-27-2]
Corticotropin-releasing factor (human) [86784-80-7]
Corticotropin-releasing factor (sheep) [79804-71-0]
Cyclosporin A [59865-13-3]
Daptomycin [103060-53-3]
Delta sleep-inducing peptide (rabbit) [62568-57-4]
Dermorphin [77614-16-5]
Didemnin A [77327-04-9]
Dynorphin A (swine) [80448-90-4]
Dynorphin B (swine) [83335-41-5]
Echinocandin B [54651-05-7]
Eledoisin [69-25-0]
α-Endorphin (sheep) [59004-96-5]β-Endorphin (sheep) [59887-17-1]
Endothelin 1 (swine) [117399-94-7]
Endothelin 1 (swine reduced) [114640-06-1]
Continued on next page

13

Fibrinopeptide A (human) [25422-31-5]
Galanin (swine) [88813-36-9]
Gastric inhibitory polypeptide (swine major) [11063-17-5]
Glucagon (swine) [16941-32-5]
Glucagon-like peptide 1 (Rana catesbeiana) [116186-51-7]
Glucagon-like peptide I (human) [87805-34-3]
Gramicidin A [11029-61-1]
Gramicidin S [113-73-5]
Insulin (cattle) [11070-73-8]
Insulin (cattle-A reduced) [17289-65-5]
Insulin (cattle-B reduced) [16941-47-2]
Insulin (human) [11061-68-0]
Insulin (human-A reduced) [24800-07-5]
Insulin (human-B reduced) [27597-36-0]
Insulin (swine) [12584-58-6]
Kallidin [342-10-9]
Luteinizing hormone-releasing factor (swine) [33515-09-2]
Magainin I [108433-99-4]
Mast cell degranulating peptide (Vespula lewisii) [72093-21-1]α-Melanotropin (swine) [581-05-5]
Melittin (honeybee) [20449-79-0]
Motilin (swine) [9072-41-7]
Neuropeptide Y (human) [90880-35-6]
Neuropeptide Y (swine) [83589-17-7]
Neurotensin (cattle) [55508-42-4]
Nisin A [1414-45-5]
Oxytocin [50-56-6]
Phalloidin [17466-45-4]
Pneumocandin A0 [120692-19-5]
Pneumocandin B0 [135575-42-7]
Polymyxin B1 [4135-11-9]
Polymyxin E1 [7722-44-3]
Ramoplanin A 1 [81988-87-6]
Ramoplanin A 1 (peptide moiety) [123961-33-1]
Secretin (swine) [17034-35-4]
Somatoliberin (human pancreatic islet) [83930-13-6]
Somatostatin (sheep) [38916-34-6]
Somatostatin (sheep reduced) [40958-31-4]
Somatostatin-28 (sheep) [73032-94-7]
Somatostatin-28 (sheep reduced) [75306-06-8]
Substance P [33507-63-0]

Continued on next page14

Thymosin α1 (cattle) [62304-98-7]
Thymosin β4 (cattle) [77591-33-4]
Transforming growth factor α (rat) [89899-53-6]
Transforming growth factor α (rat reduced) [89747-89-7]
Valinomycin [2001-95-8]
Vasoactive intestinal octacosapeptide (swine) [40077-57-4]
Vasopressin [11000-17-2]
Virginiamycin S1 [23152-29-6]

15

CA Index Name Locant Rules

1.1 Geneva
Suffixes

Locants are not cited for Geneva suffixes denoting acid, acid halide or
halogenide, amide, nitrile, or aldehyde functional groups that terminate one orboth ends of a chain.
Octadecanoic acid
Butanediamide
Under former policy, an exception was sometimes made for a Geneva suffix
that terminated one end of a heteroacyclic chain assigned an organic
replacement name. Because replacement prefixes were preferred tofunctional suffixes for lowest locants, the Geneva suffix could end up on thehigh-numbered end of the chain, necessitating the use of a locant. This
exception has been eliminated, because in an organic replacement name for aheteroacyclic chain lowest locants are assigned to functional suffixes, notreplacement prefixes. When that functional suffix is a single Geneva suffix, it
will always have an implied locant of “1”.
New: 3,7,9-Trioxa-8-siladecanal
9CI: 2,4,8-Trioxa-3-siladecan-10-al

1.2 Conjunctive
Suffixes

A locant is not cited for a single conjunctive suffix on benzene or a saturated
homogeneous monocyclic ring.
Benzeneethanol
Cyclohexanepropanoic acidFor all other conjunctive suffixes, a locant is cited to denote the position of
attachment to the ring.
New: 1,1,2,2,3,3-Cyclopropanehexamethanol
9CI: Cyclopropanehexamethanol
New:
9CI:

2-Cyclohexene-1-acetaldehyde
2-Cyclohexeneacetaldehyde

161.3 Other
Functional
Suffixes

For functional suffixes that are not Geneva (oic acid, amide, etc.) suffixes andnot part of conjunctive suffixes, locants are cited.
New: 1-Disiloxanol
9CI: Disiloxanol
New:
9CI:

1,2-Ethanediimine
Ethanediimine

New:
9CI:

1,2-Diazenedicarboxylic acid
Diazenedicarboxylic acid

New:
9CI:

1,2,3,4,5-Benzenepentacarbonitrile
Benzenepentacarbonitrile

New: 2-Oxiranecarboxylic acid
9CI:
Oxiranecarboxylic acid
New: Bicyclo[2.2.2]octan-2-one
9CI:
Bicyclo[2.2.2]octanone17

2. Subtractive
Suffixes

A locant is not cited for a subtractive suffix denoting unsaturation if the suffix
is for a single site of unsaturation on one of the following:• A homogeneous molecular skeleton parent with two skeletal atoms (with orwithout a functional suffix) or a parent radical derived therefrom.
Ethynamine
Diazene1,2-diphosphenediyl• A homogeneous monocyclic ring parent with no functional or conjunctive
suffix.
Cyclooctene
Cyclotetrasilene
For all other double and triple bonds, locants are cited.

3. Free
Valences

New:
9CI:

2-Propynoic acid
Propynoic acid

New:
9CI:

1-Triazene
Triazene

New:
9CI:

1,3-cyclobutadien-1-yl
cyclobutadien-1-yl

A locant is not cited for a free valence if the radical is one of the following:• An acyclic radical with only one possible site of attachment, or whose siteof attachment is implicit in the radical name itself. Among the many
examples that could be cited are the following:
acetylchloromethyleneamino
ethoxynitro
arsinothioyl
iminophosphono
benzoylmethylsulfonimidoyl• A radical derived from a saturated homogeneous molecular skeleton parent
with two or more skeletal atoms by the loss of one or more hydrogen atoms
from one terminal atom.
hexyl
pentasilanyl
ethylidyne
diphosphinylidene
Continued on next page18

• A radical derived from an unsaturated homogeneous molecular skeleton
parent with two skeletal atoms by the loss of one or more hydrogen atoms
from one terminal atom.
diazenylethenylidene• A radical derived from a homogeneous chalcogen molecular skeleton parent
or parent oxide, with either one or two free valences.
dioxy
disulfonyl• A radical derived from a saturated homogeneous monocyclic ring parent by
the loss of one or more hydrogen atoms from one skeletal atom.
cyclopentyl
cyclotrisilanylidene• A radical derived from a heterocyclic ring parent not assigned an organic
replacement name and with a single heteroatom that is cationic and the siteof the free valence.
oxiranio
3H-indolio• A phenyl radical, either substituted or unsubstituted.
For all other radicals, locants are cited for the free valences.
New: 1-disilazanyl
9CI
disilazanyl
New:
9CI

1,2-ethanediylidene
ethanediylidene

New: 2-propen-1-yl
9CI:
2-propenyl
New: 2-oxiranylidene
9CI:
oxiranylidene
New:
9CI:

2-pyrazinyl
pyrazinyl

New:
9CI:

cyclotrisiloxan-2-yl
cyclotrisiloxanyl

19

4.1 Substituent
Prefixes:
Multiplying
Radicals

Locants are cited for every multiplying radical to denote the points ofattachment to each occurrence of the parent.
Methane, 1,1'-oxybisAcetic acid, 2,2'-thiobisHydrazine, 1,1'-methylenebisIf the multiplied parent has other substituent prefixes besides the multiplying
radical, locants are cited for those as well.
New:
9CI:

Methane, 1,1'-oxybis[1-chloroMethane, 1,1'-oxybis[chloro-

The same rules apply without exception to radicofunctional parents.
New: Hydroperoxide, 1,1'-[oxybis(methylene)]bis9CI: Hydroperoxide, [oxybis(methylene)]bisNew:
9CI:

Nitroxide, N,N'-1,4-phenylenebis[N-ethenyl
Nitroxide, 1,4-phenylenebis[ethenyl-

New:
9CI:

Disulfide, 1,1'-(1,2-ethanediyl)bis[2-(1-naphthalenyl)Disulfide, 1,2-ethanediylbis[1-naphthalenyl-204.2 Other
Substituent
Prefixes

For a substituent prefix other than a multiplying radical, a locant is not cited if
the substituent prefix is one of the following:• One or more substituent prefixes on a single occurrence of a mononuclear
molecular skeleton parent or parent oxide, sulfide, selenide, or telluride.
Methane, dichloroPhosphine oxide, triphenylSilane, tetramethyl• One or more substituent prefixes on a single occurrence of a mononuclear
molecular skeleton parent with an attached functional suffix, provided thatsuffix has no substitutable hydrogens and no alcohol or acid hydrogens.
Methanone, diphenylSilanecarbonitrile, trimethyl• One or more substituent prefixes on a single occurrence of a mononuclear
nitrogen parent.
Nitroxide, methylene
Amidogen, difluoro• One or more substituent prefixes on a mononuclear radical all of whose
substitutable hydrogens are on a single atom.
trifluoromethyl
dimethylphosphino
diphenylphosphinothioyl
methylcarbonimidoyl
diphenylamino
cyclohexylimino• A single substituent prefix on a single occurrence of a saturated or
unsaturated homogeneous molecular skeleton parent with two skeletal
atoms and no functional suffix.
Hydrazine, bromoEthyne, chloro• One or two substituent prefixes on a single occurrence of a homogeneous
chalcogen molecular skeleton parent or two substituent prefixes on a single
occurrence of the parent oxide.
Hydroperoxide, phenyl
Disulfone, dimethyl

Continued on next page21

• A single substituent prefix on a single occurrence of a homogeneous
monocyclic ring parent with no functional suffix.
Benzene, methylTriaziridine, nitroCycloheptatrienylium, methylFor all other substituent prefixes, locants are cited.
New: Methanol, 1-chloro9CI: Methanol, chloro-

New:
9CI:

Disiloxane, 1-ethylDisiloxane, ethyl-

New: Methanesulfonic acid, 1,1,1-trifluoro9CI: Methanesulfonic acid, trifluoroNew:
9CI:

Benzene, 1,2,3,4,5,6-hexamethylBenzene, hexamethyl-

New: Pyrazine, 2-butyl9CI: Pyrazine, butyl-

New: 2,3,4,5,6-pentafluorophenyl
9CI: pentafluorophenyl

New:
9CI:

2-iodoacetyl
iodoacetyl

New: Butanedioic acid, 2-sulfo9CI: Butanedioic acid, sulfo-

New: Propanedinitrile, 2-oxo9CI: Propanedinitrile, oxo-

New: 2-oxoethylidene
9CI: oxoethylidene

New: Ethynol, 2-bromo9CI: Ethynol, bromo-

New: 2-(2-quinolinyl)ethynyl
9CI: 2-quinolinylethynyl

New: Diazene, 1,2-diiodo9CI: Diazene, diiodo-

New: Cyclotrisiloxane, 2-methylene9CI: Cyclotrisiloxane, methyleneAll substituent prefixes on functional parent compounds—with the exceptionof formaldehyde— require heteroatom locants.
New: Carbamic acid, N,N-dimethyl9CI: Carbamic acid, dimethylNew: Diphosphonic dichloride, P,P'-diphenyl9CI: Diphosphonic dichloride, diphenylNew: Imidodisulfamide, N,N',N',N'',N''-pentaethyl9CI: Imidodisulfamide, pentaethyl-Continued on next page

22

BUT
New: Formaldehyde, nitro9CI: Formaldehyde, C-nitroAll substituent prefixes on hydrazides, hydrazones, and oximes will require
locants.
New: 2-(phenylmethylene)hydrazide
9CI: (phenylmethylene)hydrazide
New: 2-phenylhydrazone
9CI: phenylhydrazone
New: O-benzoyloxime
9CI:
benzoyloxime
4.3 Prefixes
with Greek andCapitalic
Locants

When a Greek or capitalic letter locant occurs only once in a structure, it
requires no superscript or prime when it is cited in the name.
Benzenemethanamine, N,N-dimethyl-α,α-diphenylBut multiple occurrences of the same Greek or capitalic letter locant in a
structure must be distinguished because they refer to different positions on theparent. In the new system, Greek and capitalic letter locants with superscript
Arabic numerals are now preferred to primed and unprimed locants.
New: 1,2-Benzenediacetic acid, α 1,α 2-diamino9CI: 1,2-Benzenediacetic acid, α,α '-diaminoNew: 1,2-Ethanediamine, N1,N2-dimethyl9CI: 1,2-Ethanediamine, N,N'-dimethylNew: Butanediamide, N1-phenyl9CI: Butanediamide, N-phenylBut primes must be used if Arabic numerals are not available. For example,
if the parent is a functional parent compound.
Imidodicarbonimidic diamide, N,N,N',N',2-pentamethyl-Continued on next page23

And primes alone are used if Arabic numerals are available but are the samefor each Greek or capitalic letter locant.
1,1-Cyclopropanedimethanol, α,α’-dimethylEthanimidamide, N,N'-diphenylPrimes are combined with superscript Arabic numerals if (1) the parent
includes a ring assembly or other ring with primed locants, (2) a multiplying
radical is attached at positions whose locants include superscript Arabic
numerals, or (3) the same primed locant occurs at different positions on theparent.
New: [1,1'-Biphenyl]-4,4'-diacetic acid, α 4,α4'-dihydroxy9CI: [1,1'-Biphenyl]-4,4'-diacetic acid, α,α'-dihydroxyNew: 1,4-Benzenediamine, N1, N1'-1,6-hexanediylbis[N4-methyl9CI: 1,4-Benzenediamine, N,N''-1,6-hexanediylbis[N'-methylNew: 1,3-Benzenedicarboximidamide, N'1,N'3-diphenyl-, [C1(Z),C3(Z)]9CI:
1,3-Benzenedicarboximidamide, N',N'''-diphenyl-, [C(Z),C'(Z)]Examples of the
Changes

1

Me

O

HC
3

CH
2

R

New: 3-methyl-2-oxiranyl9CI: 3-methyloxiranylNHMe
NHMe

NO2

New: 1,2-Benzenediamine, N1,N2-dimethyl-3-nitro9CI: 1,2-Benzenediamine, N,N'-dimethyl-3-nitro-

Continued on next page

24

HO2C

CH2

CH2

CO2Et

CH2

CO2Et

New: Butanedioic acid, 1-ethyl ester
9CI: Butanedioic acid, monoethyl ester
Cl
HO2C

CH

New: Butanedioic acid, 2-chloro-, 3-ethyl ester
9CI: Butanedioic acid, chloro-, 1-ethyl ester
R

N

N

R

New: 1,2-hydrazinediylidene
9CI: azinoO
Et

O

C

O
NH

CH2

NH

C

O

New: Carbamic acid, N,N'-methylenebis-, O,O'-diethyl ester
9CI: Carbamic acid, methylenebis-, diethyl ester

25

Et