Skip to content
Dabour HubLEARN · PRACTICE · EXPLORESign inStudent

3.1.3Physical Chemistry

Nomenclature — AQA AS Chemistry Revision Notes & Topical Questions

5 min read 5 parts Lesson 66 of 102

📚 AQA AS Chemistry Hub / Topical Revision
🩺
100% Curriculum Specification Match Lesson Doctor Verified
The only platform with 100% curriculum specification match and verified interactive question banks.
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
0%read

Part 1 of 5Building a Name

A systematic name is built from the longest chain, the functional group and any side groups.

1
Find the longest continuous carbon chain that includes the functional group, and choose the stem name from it.
2
Number the chain from the end that gives the lowest numbers to the functional group, then to other substituents.
3
Name each branch or halogen as a prefix with its position number, such as 2-methyl or 1-bromo.
4
List prefixes in alphabetical order, ignoring di-, tri- and tetra-, and use these multipliers for repeated groups.
5
Add the correct ending: -ane, -ene, -ol, or -oic acid, with a position number for the functional group where needed.

Part 2 of 5Stems and Endings

Alkanes
  • Alkanes Use the ending -ane, for example propane, CH₃CH₂CH₃, and name branches with prefixes such as methyl.
Alkenes
  • Alkenes Use -ene with the position of the double bond, for example but-1-ene, CH₂=CHCH₂CH₃.
Alcohols
  • Alcohols Use -ol with the carbon number of the –OH group, for example propan-2-ol, CH₃CH(OH)CH₃.
Halogenoalkanes
  • Halogenoalkanes Use the prefix chloro-, bromo- or iodo- with a position number, for example 2-bromopropane.
CarbonsStemCarbonsStem
1meth-4but-
2eth-5pent-
3prop-6hex-

Part 3 of 5Naming Rules in Practice

Naming Rules in Practice
Alkyl groups
  • Alkyl groups Alkane branches have the ending -yl, such as methyl (CH₃–) and ethyl (C₂H₅–).
Multiple groups
  • Multiple groups Use di-, tri-, or tetra- for repeats, with a position number for each, as in 2,2-dimethylpropane.
Punctuation
  • Punctuation Use commas between numbers, hyphens between numbers and letters, and write the name as one word.
Tie-break
  • Tie-break If numbering gives the same set of numbers from either end, the group that comes first alphabetically gets the lower number.

Part 4 of 5Worked Example

Question Name the compound CH₃CH(CH₃)CH₂CHClCH₃.

  1. The longest chain contains five carbons, so the stem is pent-, and the compound is a pentane.
  2. Numbering from the rightthe Cl is on carbon 2, and the methyl is on carbon 4.
  3. Numbering from the left would give methyl 2 and chloro 4: the same set of numbers {2, 4}.
  4. Tie-breakalphabetically chloro comes before methyl, so chloro gets the lower number.

Answer 2-chloro-4-methylpentane

Part 5 of 5Exam Checklist & Tips

3.1.3 – Key Points for the Exam

  • IUPAC The international body that sets rules for the systematic naming of chemical compounds.
  • Alkyl group A side chain derived from an alkane by removing one hydrogen, such as methyl.
  • Stem The part of the name that shows the number of carbon atoms in the longest chain.
  • Substituent An atom or group that replaces a hydrogen on the main carbon chain.

Common Mistakes

  • Choosing a chain that is not the longest one possible, or one that misses the functional group.
  • Numbering from the wrong end, giving higher locants than necessary.
  • Putting substituents in order of position number instead of alphabetical order.
  • Forgetting position numbers for the functional group in chains of three or more carbons.

Last updated:

\n