Order of Precedence of Groups
When compounds contain more than one functional group, the order of precedence determines which groups are named with prefix or suffix forms. The highest precedence group takes the suffix, with all others taking the prefix form. However, double and triple bonds only take suffix form (-en and -yn) and are used with other suffixes.
Prefixed substituents are ordered alphabetically (excluding any modifiers such as di-, tri-, etc.), e.g. chlorofluoromethane, not fluorochloromethane. If there are multiple functional groups of the same type, either prefixed or suffixed, the position numbers are ordered numerically (thus ethane-1,2-diol, not ethane-2,1-diol.) The N position indicator for amines and amides comes before "1", e.g. CH3CH(CH3)CH2NH(CH3) is N,2-dimethylpropanamine.
| Priority | Functional group | Formula | Prefix | Suffix |
|---|---|---|---|---|
| 1 | Cations e.g. Ammonium |
NH4+ |
-onio- ammonio- |
-onium -ammonium |
| 2 | Carboxylic acids
|
–COOH –COSH –COSeH –SO3H –SO2H |
carboxy- sulfanylcarbonyl- selanylcarbonyl- sulfo- sulfino- |
-oic acid* -thioic S-acid* -selenoic Se-acid* -sulfonic acid -sulfinic acid |
| 3 | Carboxylic acid derivatives
|
–COOR –COX –CONH2 –CON=C< –C(=NH)NH2 |
R-oxycarbonyl- halocarbonyl- carbamoyl- -imido- amidino- |
-R-oate -oyl halide* -amide* -imide* -amidine* |
| 4 | Nitriles Isocyanides |
–CN –NC |
cyano- isocyano- |
-nitrile* isocyanide |
| 5 | Aldehydes Thioaldehydes |
–CHO –CHS |
formyl- thioformyl- |
-al* -thial* |
| 6 | Ketones
|
=O =S =Se =Te |
oxo- sulfanylidene- selanylidene- tellanylidene- |
-one -thione -selone -tellone |
| 7 | Alcohols
|
–OH –SH –SeH –TeH |
hydroxy- sulfanyl- selanyl- tellanyl- |
-ol -thiol -selenol -tellurol |
| 8 | Hydroperoxides
|
-OOH -SOH -SSH |
hydroperoxy- hydroxysulfanyl- disulfanyl- |
-peroxol -SO-thioperoxol -dithioperoxol |
| 9 | Amines Imines Hydrazines |
–NH2 =NH –NHNH2 |
amino- imino- hydrazino- |
-amine -imine -hydrazine |
| 10 | Ethers Thioethers Selenoethers |
–O– –S– –Se– |
-oxy- -thio- -seleno- |
|
| 11 | Peroxides Disulfides |
–OO– –SS– |
-peroxy- -disulfanyl- |
Read more about this topic: IUPAC Nomenclature Of Organic Chemistry
Famous quotes containing the words order, precedence and/or groups:
“A wise man should order his interests, and set them all in their proper places. This order is often troubled by greed, which puts us upon pursuing so many things at once that, in eagerness for matters of less consideration, we grasp at trifles, and let go things of greater value.”
—François, Duc De La Rochefoucauld (1613–1680)
“What is line? It is life. A line must live at each point along its course in such a way that the artist’s presence makes itself felt above that of the model.... With the writer, line takes precedence over form and content. It runs through the words he assembles. It strikes a continuous note unperceived by ear or eye. It is, in a way, the soul’s style, and if the line ceases to have a life of its own, if it only describes an arabesque, the soul is missing and the writing dies.”
—Jean Cocteau (1889–1963)
“As in political revolutions, so in paradigm choice—there is no standard higher than the assent of the relevant community. To discover how scientific revolutions are effected, we shall therefore have to examine not only the impact of nature and of logic, but also the techniques of persuasive argumentation effective within the quite special groups that constitute the community of scientists.”
—Thomas S. Kuhn (b. 1922)