There are different ways to present a hydrocarbon with carbon skeletons but there's only a special way to name them! Let's learn naming & formulae of hydrocarbon in A-Level Chemistry.
Basic definitions:
Hydrocarbon: compound consisting of carbon and hydrogen only
Saturated: contains single carbon-carbon bonds only
Unsaturated: contains a carbon=carbon bond
Homologous series: a family of organic compounds with the same functional group and general formula. There is gradual change in the physical properties with the same chemical properties. Each successive member differs by CH2.
Functional group: an atom or group of atoms that when present cause molecules to have similar chemical properties
Formulae
Molecular formula: shows the actual number of each type of atom
Empirical formula: shows the simplest whole number ratio of atoms of each element in a compound
General formula: shows the algebraic formula for a homologous series
Structural formula: show minimal detail of the arrangements of atoms in a molecules
Displayed formula: shows all elements and bonds present in a molecule
Skeletal formula: simplified organic formula, removed hydrogen atoms from alkyl chains leaving only the carbon skeleton and associated functional groups
Carbon skeletons
Aliphatic: a compound containing carbon and hydrogen, joined in straight chains, with branches – no aromatic rings
Alicyclic: an aliphatic compound arranged in non-aromatic rings with or without side chains
Aromatic: compound containing a benzene ring
Nomenclature
1. Count longest carbon chain and name appropriately
2. Find any branched chains and count how many carbons they contain
3. Add the appropriate prefix for each branched chain
- If there are two or more functional groups di, ortri, tetra, penta need to be used.
- When numbering carbons, the functional group needs to be on the lowest number carbon.
- Words and numbers are separated by dashes, numbers are separated by commas.
- If there is more than one different functional group or side chain, the groups are listed in alphabetical order – ignoring di,tri.
- Alkenes: the double bond will be between two carbons, always use the lowest number
- Alcohols: if there is an -OH bond in the chain then the prefix hydroxy- should be used.
- Esters: have two parts in their names from an alcohol and a carboxylic acid.
Isomers
Structural isomers: same molecular formula but different structures
Types of isomer:
· Chain isomers: same molecular formula but different structures in the carbon skeleton (have branches)
· Positional isomers: functional group is in a different place
· Functional group isomers: same molecular formula with differing functional groups, e.g. alcohol or an ether; cycloalkane or analkene
Drafted by Eunice (Chemistry)
References:
- https://www.facebook.com/BCP100/photos/a.533626306674918/3278162228887965/?type=3
- https://www.savemyexams.co.uk/igcse-chemistry-edexcel-new/revision-notes/organic-chemistry-introduction/organic-compounds-hydrocarbons/
- https://slidetodoc.com/the-molecules-of-life-chapter-3-the-simplest/
- https://www.facebook.com/Jllne/posts
- https://www.pinterest.co.uk/pin/333055334926419796/