How to name alcohols and write their formulas

Note: There’s a summary table at the end of this page.

Definitions

Organic: Contains carbon

Hydrocarbons: Organic compounds made from hydrogen and carbon only

Alcohol: Organic compounds that come from crude oil

Homologous series: A series of compounds with the same functional group and similar chemical properties

Functional group: It is added to a compound to change its reactivity (eg. Functional group of alcohols: -OH <- IMPORTANT)

What are alcohols?

Ethanol: alcohol found naturally in fermented sugar. In a closed container with bacteria that do anaerobic respiration, ethanol is a side product.

Uses of alcohol:

• Fuels
• Solvents
• Ethanol in alcoholic drinks

General formula

General formula for alcohols: C_nH_2n+1OH

Each homologous series has its own general formula.

To use the general formula, replace n in the general formula with the number of C (carbon) atoms.
eg. An alcohol compound with 2 carbon atoms:

C_nH_2n+1OH
= C₍₂₎H₂₍₂₎₊₁OH
= C₂H₈OH

How to name alcohols

Every alkane ends with “-anol”, but starts differently depending on the number of C (carbon) atoms.

1 – meth
2 – eth
3 – prop
4 – but
5 – pent
6 – hex

eg. An alcohol compound with 3 carbon atoms: propanol

Here’s a trick I use to remember how each compounds starts:
(1) Monkeys (2) Eat (3) Peanut (4) Butter
5 & 6 are easy enough to remember because they are the same as shapes (pentagon, hexagon)

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However… From 4 carbons and up, we need to add something extra:

Eg. you get butan-1-ol and butan-2-ol.

• The number shows where the -OH is
  • You start counting from the side of the double bond
  • If it is exactly in the middle, you can count from any side

Displayed / structural formula

Important:

H (Hydrogen) has 1 bond
C (Carbon) has 4 bonds
O (Oxygen) has 2 bonds
(This will help you draw the structure)

Steps:

1. Draw a chain with the correct number of C’s (carbons).
2. Add H’s (hydrogens) around the C’s (carbons) to make each carbon have 4 bonds, except for the last C.
3. Add an O (oxygen) and an H (hydrogen) to the end of the chain.
4. Ensure that the lines are drawn in and that each letter has the correct number of bonds.

Summary

Have any questions about this topic? Leave an anonymous comment below and I’ll get back to you 🙂