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 showing an overview of key organic reactions including pathways between amine, alkane, halogenoalkane, alkene, diol, alcohol, aldehyde, ketone, carboxylic acid, ester, ammonium salt, and carboxylate salt.
ReactionReagent and conditionsReaction type
1Halogen, UV lightFree radical substitution
2H2, Ni or Pt catalyst, heatElectrophilic addition
3Al2O3 catalyst, heatThermal decomposition
4Hydrogen halide or halogenElectrophilic addition
5NaOH in ethanol, refluxElimination
6Conc. NH3 in ethanol, heat under pressureNucleophilic substitution
7KCN in ethanol, refluxNucleophilic substitution
8Dilute HCl(aq)Acid-base
9NaOH(aq), refluxNucleophilic substitution
10Hydrogen halide, PCl5 or SOCl2 OR KCl and conc. acid OR PCl3 and heatNucleophilic substitution
11Steam, H3PO4 catalyst, 300°C, 60 atmElectrophilic addition
12Conc. H2SO4 or Al2O3 catalyst, heatElimination
13Cold, dilute acidified KMnO4(aq)Oxidation
14K2Cr2O7(aq) or KMnO4(aq), H2SO4 catalyst, refluxOxidation
15NaBH4(aq) or LiAlH4 in dry ether, heatNucleophilic addition
16K2Cr2O7(aq) or KMnO4(aq), H2SO4 catalyst, distillOxidation
17HCN, KCN catalyst, heatNucleophilic addition
18Dilute HCl(aq) or dilute NaOH(aq), heatHydrolysis
19Carboxylic acid, conc. H2SO4Condensation
20H2O, dilute HCl(aq), heatHydrolysis
21LiAlH4 in dry ether, heatReduction
22Dilute HCl(aq), heatHydrolysis
23Alcohol, conc. H2SO4Condensation
24Dilute NaOH(aq)Acid-base

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, oxidation
AlcoholO-HPolar O-H bondNucleophilic substitution, elimination, oxidation, condensation
HalogenoalkaneC-XPolar C-X bondNucleophilic substitution, elimination
Aldehyde/KetoneC=OPolar C=O bondOxidation (aldehydes only), reduction, nucleophilic addition
Carboxylic acidCOOHElectron deficient CCondensation, reduction
EsterRCOOR’Electron deficient CHydrolysis

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