4.1.1 - Organic: Basic Concepts

Hydrocarbon

A compound containing only carbon and hydrogen

Saturated compound

Contains only single carbon–carbon (C–C) bonds

Unsaturated compound

Contains multiple C–C bonds (C=C, C≡C or aromatic rings)

Molecular formula

Shows the actual number of each type of atom in a molecule

Empirical formula

Shows the simplest whole-number ratio of atoms in a compound

General formula

Algebraic formula representing a homologous series (e.g. CₙH₂ₙ)

Structural formula

Shows how atoms are arranged with minimal detail (e.g. CH₃CH₂CH₃)

Displayed formula

Shows all atoms and all covalent bonds in a molecule

Skeletal formula

Simplified representation showing carbon skeleton and functional groups only

Carbon bonding rule

Each carbon forms 4 covalent bonds

Alkane shape

Tetrahedral around carbon with bond angle 109.5°

Aliphatic compound

Carbon and hydrogen in straight chains, branched chains or non-aromatic rings

Alicyclic compound

Aliphatic compound arranged in non-aromatic rings

Aromatic compound

Compound containing a benzene ring

Homologous series

(series of compounds with the) same functional group

OR similar chemical properties ✔

each successive / subsequent member differing by CH2 ✔

Homologous series – CH₂ difference

Each member differs from the next by CH₂

Homologous series – properties

Same chemical properties, gradual change in physical properties

Functional group

Atom or group of atoms responsible for characteristic reactions

Alkane functional group

C–C single bond

Alkane suffix

-ane

Alkene functional group

C=C double bond

Alkene suffix

-ene

Alcohol functional group

–OH

Alcohol suffix

-ol

Alcohol prefix

hydroxy-

Haloalkane functional group

C–halogen

Haloalkane prefixes

fluoro-, chloro-, bromo-, iodo-

Aldehyde functional group

–CHO

Aldehyde suffix

-al

Ketone functional group

C=O

Ketone suffix

-one

Carboxylic acid functional group

–COOH

Carboxylic acid suffix

-oic acid

Ester functional group

–COO–

Ester suffix

-yl alkanoate

Functional group priority

Carboxylic acids > aldehydes > ketones > alcohols > alkenes > halogenoalkanes

Naming priority rule

Highest priority group takes the suffix and lowest number

Alkene naming rule

Double bond gets lowest possible number

E/Z notation

Used to describe alkene stereoisomers

Branched chain naming

Branches named as alkyl groups (e.g. methyl, ethyl)

Lowest number rule

Number chain to give functional group lowest possible number

Alphabetical order rule

List substituents alphabetically (ignore di-, tri-)

Number punctuation

Numbers separated by commas, words by hyphens

Suffix vowel rule

If suffix starts with vowel, remove “e” from alkane stem

Multiple identical groups

Use di-, tri-, tetra-, penta-, hexa-

Aldehyde position

Always on carbon 1 (no number needed)

Carboxylic acid position

Always on carbon 1 (no number needed)

Diacid naming

Two –COOH groups → dioic acid

Alcohol priority

–OH has higher priority than alkenes and haloalkanes

Hydroxy prefix rule

Used when –OH is not the highest priority group

Ester name origin

Alkyl from alcohol + alkanoate from carboxylic acid

Structural isomers

Same molecular formula, different structural formulae

Chain isomerism

Different carbon skeletons

Position isomerism

Same skeleton, functional group in different positions

Functional group isomerism

Same formula, different functional groups

Cycloalkanes general formula

CₙH₂ₙ

Alkene general formula

CₙH₂ₙ

Cycloalkane vs alkene

Same molecular formula, different functional groups

Homolytic fission

each atom gets one e- from covalent bond

forming 2 free radicals

Free radical

Species with an unpaired electron

Heterolytic fission

1 atom gets both electrons

producing ions

Arrow in heterolytic fission

Two-headed arrow shows movement of an electron pair

Organic reaction type

Most occur via heterolytic fission

Curly arrow meaning

Shows movement of an electron pair

Curly arrow start

Starts from a lone pair or a bond

Stereoisomers

(Compounds with the) same structural formula but a different arrangement (of atoms) in space