Year 1 Synthetic Routes

This lesson covers: 

  1. What synthetic routes are and why they are important
  2. The key organic reactions covered so far
  3. How functional groups determine reactivity

Synthetic routes map out synthetic pathways

Chemists create complex compounds, which are often used in medicines or agricultural chemicals.

Typically, it's not feasible to synthesise the target compound directly from a single starting material in one step.

A synthetic route outlines the sequence of reactions needed to transform starting materials into the desired end product.


It details:

  • Every chemical intermediate formed along the way.
  • The specific reagents and conditions required at each stage of the process.


For instance, converting 2-chloropropane to propanone isn't a straightforward, one-step process.


Instead, a two-step synthetic route is necessary:

Diagram showing the synthetic route from 2-chloropropane to propanone through intermediate propan-2-ol.
  1. 2-chloropropane reacts with KOH, producing propan-2-ol.
  2. Propan-2-ol, when treated with acidified K2Cr2O7, yields propanone.

Summary of key organic reactions

Below is an overview of the primary types of organic reactions we've discussed:

Diagram summarising key organic reactions including alkanes, alkenes, halogenoalkanes, alcohols, aldehydes, carboxylic acids, amines, nitriles, and ketones.
ReactionReagent and conditionsReaction type
1Halogen, UV lightFree radical substitution
2H2, Ni catalyst, 150°CElectrophilic addition
3Zeolite catalyst, heatThermal decomposition
4Hydrogen halide or halogenElectrophilic addition
5KOH in ethanol, refluxElimination
6Conc. NH3 in ethanol, heat under pressureNucleophilic substitution
7KCN in ethanol, refluxNucleophilic substitution
8NaOH(aq), refluxNucleophilic substitution
9Steam, H3PO4 catalyst, 300°C, 60 atmElectrophilic addition
10Conc. H2SO4 catalyst, heatElimination
11K2Cr2O7(aq), H2SO4 catalyst, refluxOxidation
12K2Cr2O7(aq), H2SO4 catalyst, distillOxidation

Functional groups dictate reactivity

The behaviour and properties of functional groups significantly affect molecular reactions.


For example:

  • Nucleophiles are attracted to the partially positive carbon in halogenoalkanes, but they don't target the electron-rich C=C double bond in alkenes.
  • Alcohols, due to their polar O-H bond and the lone pair of electrons on the oxygen atom, can act as nucleophiles.


The following table outlines common reactions associated with key functional groups:

Homologous seriesFunctional groupPropertiesTypical reactions
AlkaneC-CNonpolar, unreactiveFree radical substitution
AlkeneC=CNonpolar, electron-richElectrophilic addition
AlcoholO-HPolar O-H bondOxidation, elimination
HalogenoalkaneC-XPolar C-X bondNucleophilic substitution
Aldehyde/KetoneC=OPolar C=O bondOxidation (aldehydes only)

Compounds with multiple functional groups require the identification of all such groups to accurately predict their reactivity.