Chemistry · General chemistry II · Worked example
Name a branched alcohol
Name (CH₃)₂CHCH₂CH₂OH.
Find the chain with the –OH carbon
The longest chain containing the carbon with the –OH group has four carbons: butanol.
Number from the –OH end
Numbering from the –OH end puts it at carbon 1 and the methyl group at carbon 3. From the other end they would be at 4 and 2, and the –OH comes first in deciding.
Write the name
The methyl group’s number and name come first, then the –OH number and the parent name.
Result
3-methyl-1-butanol (today’s IUPAC form: 3-methylbutan-1-ol).
Your turn
Name the ketone CH₃CH₂CH₂COCH₃.
Show the answer and explanation
2-pentanone (pentan-2-one).
Five carbons with the carbonyl group on carbon 2 from the nearer end. 4-pentanone numbers from the wrong end, and pentanal would put the carbonyl group at the end of the chain.
Keep exploring
Draw it with the target 2-methyl-4-butanol and turn Check on: the name describes the structure, but it numbers from the wrong end.
Return to the concept →Sources and scope
Authored study material. Tool results depend on the stated inputs and model assumptions.
Try in the workspace
Open the example inputs, change a value and keep a useful result on your board.
Draw it and check the name Check the name 2-methyl-4-butanol See 3-methyl-1-butanol in every representation Open worked example on a board Organic nomenclature in Chemistry ReferenceYour existing work stays on this device. Examples open as editable copies.