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A name is stem, locant and a suffix for the principal functional group, with every other group as a prefix; the group's own carbon counts in the chain, and esters are named as two words.
Paper packet. Every task here also exists on screen, where it is checked automatically; answers written on paper are not assessed by Nydus. When you are back at a device, enter your answers there.
You will give each group's suffix, sort formulas into classes, name chains that end in a group, combine a suffix and a prefix, name an ester, and place a ketone's locant.
You can name an alkane and know which group outranks which. A functional group's name replaces or adds to the alkane's -ane.
The principal group is the highest-priority group; it gives the suffix. Other groups are prefixes: hydroxy- (–OH), amino- (–NH2), oxo- (=O), chloro-. An ester R–COO–R′ is named as two words: the R′ group, then the acid part ending -oate.
Take ethane's two carbons and change one group:
| Group | Suffix | Example |
|---|---|---|
| alcohol –OH | -ol | ethanol, CH3CH2OH |
| aldehyde –CHO | -al | ethanal, CH3CHO |
| ketone C=O | -one | propanone, CH3COCH3 |
| carboxylic acid –COOH | -oic acid | ethanoic acid, CH3COOH |
| amine –NH2 | -amine | ethanamine, CH3CH2NH2 |
| nitrile –C≡N | -nitrile | ethanenitrile, CH3CN |
| amide –CONH2 | -amide | ethanamide, CH3CONH2 |
The group's own carbon counts in the chain: ethanal has two carbons, one of them the CHO. A group that can sit in more than one place takes a locant, placed just before the suffix: propan-1-ol, propan-2-ol; pentan-2-one, pentan-3-one. Aldehydes and acids are always on carbon 1, so they need none.
Another way: steps
To name a chain with a group:
When a molecule has two groups, only the principal group is a suffix. HOCH2CH2COOH is 3-hydroxypropanoic acid: the acid names it, and the –OH becomes hydroxy- with its number. A name never has two principal suffixes.
Esters are the exception to one-word names. They are made from an acid and an alcohol, and named in that spirit: the group from the alcohol, then the acid's name with -oic acid changed to -oate. CH3COOCH3 is methyl ethanoate; the banana-smelling CH3COOCH2CH2CH2CH2CH3 is pentyl ethanoate.
A functional group changes only the molecule's spelling. It changes the chemistry; the name records it.
The group's carbon is extra. It counts in the chain.
A molecule can have two suffixes. Only the principal group does.
Esters are one word. They are named as two.
Four carbons including the one with –OH: stem but-.
Count the group's carbon.
Number from the –OH end: it is on carbon 1.
Nearest end.
Put together, the name is butan-1-ol.
Stem, locant, suffix.
How many carbons, counting the COOH carbon?
Three: stem prop-.
What ending does an acid take, and does it need a number?
-anoic acid, no number: propanoic acid.
When an amide, –CONH2 is the highest-priority group in a molecule, what suffix ends the name?
The suffix is x.
Match each formula to the class of compound it is.
| alcohol | aldehyde | ketone | carboxylic acid | ester | |
|---|---|---|---|---|---|
| CH3CH2OH | |||||
| CH3CH2CHO | |||||
| CH3COCH3 | |||||
| CH3CH2COOH | |||||
| CH3COOCH3 |
An unbranched chain of $6$ carbon atoms, counting the group's own carbon, ends in a carboxylic acid group, –COOH. What is the compound's name?
The compound is n.
HOCH2CH2COOH has an alcohol group and a carboxylic acid group on a three-carbon chain. Which name is correct?
The smell of bananas comes largely from the ester CH3COOCH2CH2CH2CH2CH3. What is its name?
It is n.
Lesson test: one question per skill, one attempt each, no hints. Your answers are checked when you submit.
Name the ketone CH3CH2COCH2CH2CH3.
The ketone is n.
You can name a molecule by its principal group. Tell someone why HOCH2CH2COOH is an acid first and an alcohol second. Next: names that carry shape — E, Z, R and S.
8. Your turn: CH3CH2COOH, step 3