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:

Flowchart showing the summary of key organic reactions including alkanes, alkenes, halogenoalkanes, alcohols, aldehydes, ketones, and carboxylic acids.
ReactionReagent and conditionsReaction type
1Halogen, UV lightFree radical substitution
2H2, Ni catalyst, 150°CElectrophilic addition
3Hydrogen halide or halogenElectrophilic addition
4NaOH(aq), refluxNucleophilic substitution
5Sodium halide, H2SO4, refluxNucleophilic substitution
6Steam, H3PO4 catalyst, 300°C, 60 atmElectrophilic addition
7Conc. H2SO4 catalyst, heatElimination
8K2Cr2O7(aq), H2SO4 catalyst, refluxOxidation
9K2Cr2O7(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 bondNucleophilic substitution, elimination, oxidation
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.