Alkanols have the general molecular formula

Analyze the question: You are asked for the general molecular formula of alkanols (alcohols).

Explain the concept: Alkanols are derived from alkanes by replacing one hydrogen atom with a hydroxyl (-OH) group.

• Alkanes have the general formula CnH2n+2.
• Remove one H to get the alkyl group: CnH2n+1.
• Attach the -OH group: CnH2n+1OH.

Check with examples:

• n = 1: CH3OH (methanol)
• n = 2: C2H5OH (ethanol)
• n = 3: C3H7OH (propanol)

All of these fit CnH2n+1OH.

Check the other options:

• A. CnH2n-2 is the general formula for alkynes, not alkanols.
• B. CnH2n+1CHO is the formula for alkanals (aldehydes), such as CH3CHO (ethanal).
• C. CnH2n-2OH does not match any standard homologous series of alcohols.
• D. CnH2n+1OH is the correct formula for alkanols.

Tip: Remember the pattern of suffixes and formulas:

• Alkane (-ane): CnH2n+2
• Alkene (-ene): CnH2n
• Alkyne (-yne): CnH2n-2
• Alkanol (-ol): CnH2n+1OH
• Alkanal (-al): CnH2n+1CHO

"-ol" means the -OH group, so look for the formula ending in OH with the alkyl part CnH2n+1.