Chemistry SAC 4 Flashcards: Organic Chemistry

For memory

Diversity of carbon

• All 4 valence electrons available for bonding

• Forms chains & rings via single, double, or triple bonds

• Bonds with non-metals (eg. O, N, S, P, Cl)

• Forms strong, stable bonds taking lots of energy to break

Saturated hydrocarbons

A molecule which only contains single carbon-carbon bonds between atoms

Unsaturated hydrocarbons

A molecule which contains at least one double/triple bond between atoms

Bond energy

The energy (kJ) required to break 1 mole of covalent bonds in gaseous state

• The higher bond energy, the higher bond strength and stability

• The relative strength of C-C bonds explains the frequency of carbon chains on Earth.

Organic molecule representation

• Molecular: indicates the number & type of each atom present in a molecule (C4H8O)

• Structural: shows the location of atoms relative to each other, and the number and location of covalent bonds

• Semi-structural: indicates the connections in compound’s structure without showing 3D arrangement of atoms

• Skeletal: a shorthand version of structural formula, showing only C-C bonds and functional groups

Isomers

Molecules with the same number & type of atoms but different arrangements:

• Chain: different chain lengths due to branching

• Positional: branch/functional group is moved

• Stereoisomer: when groups around an atom are arranged differently

Homologous series

A family of organic molecules that have similar structures and properties, general formula, a pattern in physical properties.

Alkanes (and naming)

Saturated hydrocarbons (single C-C) with the general formula: C_nH_2n+2

Naming:

• Named with a prefix of # Cs and the suffix -ane

• Side branches are named using a prefix and -yl

• Use prefixes di, tri for multiple branches of one type

• Branch position is found by numbering each main chain C

• Give branches lowest number possible and list branches in alphabet order

• Eg. 5-methylpropane

Cycloalkane

Carbon atoms which form rings, and only single C-C bonds are present, with the general formula: C_nH_2n

• Eg. Cyclohexane (C₆H₁₂)

Alkenes (and naming)

Unsaturated hydrocarbons (double C-C) with the general formula: C_nH_2n

Naming:

• Names end in -ene

• 2Hs are lost for each C-C double bond

• Double bond position must be given the LOWEST number —> insert position before -ene

• Eg. 3,3-dimethylpent-1-ene

Degree of unsaturation

• Refers to the number of double bonds/rings in a molecule

• Calculated by: ([(2 * no of Cs)+2] - no of Hs) / 2

Benzene

An unsaturated 6C ring (C₆H₆):

• Fourth electron of each C becomes delocalized and shared by all Cs (1 ½ bonds)

• When bonded to an alkyl/functional group, it is known as a phenyl functional group (C₆H₅^-)