Synthesis of γ-tert-butyl-ε-caprolactone from oxidation of 4-tert-butylcyclohexanone

Objective

To synthesize a bulk chemical (γ-tert-butyl-ε-caprolactone) from a renewable feedstock (4-tert-butylcyclohexanone) by oxidation reaction.

Oxidation of 4-tert-butylcyclohexanone to yield γ-tert-butyl-ε-caprolactone
Oxidation of 4-tert-butylcyclohexanone to yield γ-tert-butyl-ε-caprolactone

Background

The Baeyer-Villiger oxidation is a rearrangement transformation of ketones to give esters. This is a suitable and efficient method to synthesize lactones from cyclic ketones in a one-step reaction. In this experiment, 4-tert-butylcyclohexanone is transformed into γ-tert-butyl-ε-caprolactone using m-chloroperoxybenzoic acid (m-CPBA) as the oxidizing reagent under solvent-free conditions.

Experimental procedure

To a 50 ml round-bottom flask, add 0.5 g (3.2 mmol) of 4-tert-butylcyclohexanone and 1.12 g (6.5 mmol) of m-chloroperoxybenzoic acid. Immediately attach a reflux condenser to the flask. After approximately 2 min of heating, the crude reaction will begin to become warm and will bubble. Once the reaction has begun, stir the mixture every 5 min for 30 min. After this period, treat the reaction mixture with an aqueous solution of sodium bisulfite (20 ml of 20 % NaHSO3). Transfer the mixture to a separatory funnel and rinse the reaction flask with ether (2 × 20 ml). Transfer the ether extracts again to the separatory funnel and wash with portions of an aqueous sodium bicarbonate solution (1.1 g of NaHCO3 in 200 ml of H2O) in a separatory funnel (4 × 50 ml). Dry the ether layer on anhydrous sodium sulfate Na2SO4. The desiccant is eliminated by gravity filtration on a tared round-bottom flask. Remove the ether by vacuum distillation (rotary evaporator) to give a solid residue. Wash the off-white residue with a small amount of cold pentane and collect the solid by vacuum filtration (m.p. = 57.5-58.5 ºC). Expected yields are in the 50-80 % range.

Physico-chemical properties

This table collects data for the molecular weight (Mw), melting point (M.p.) boiling point (B.p.) and density of the reactives and compounds used in this laboratory experiment.

Name Mw (g/mol) M.p. (ºC) B.p. (ºC) Density (g/ml)
Diethyl ether 74.12 -116 34.6 0.71
Hexane 86.18 -95 69 0.659
MgSO4 120.37 1124 - 1.070
NaHSO3 104.06 - - 1.48
NaHCO3 84.01 300 - 2.160
Pentane 72.15 -130 36.1 0.626
m-Chloroperbenzoic acid 172.57 69-71 - -
4-tert-Butylcyclohexanone 154.25 113-117 225.1 -
4-tert-Butyl-ε-caprolactone 170.25 57.5-58.5 - -

GHS pictograms

Hazard pictograms form part of the international Globally Harmonized System of Classification and Labelling of Chemicals (GHS) and are collected in the followinf Table for the chemical compounds used in this experiment.

Name GHS
Diethyl ether ghs02  Danger Warning Flammable pictogram ghs07  Warning Toxic cat. 4 Irritant cat. 2 or 3 Lower systemic health hazards pictogram
Hexane ghs02  Danger Warning Flammable pictogram ghs08  Danger Warning Systemic health hazards pictogram ghs07  Warning Toxic cat. 4 Irritant cat. 2 or 3 Lower systemic health hazards pictogram ghs09  Warning (for cat. 1) (for cat. 2 no signal word) Environmental hazard pictogram
MgSO4 Non-hazardous
NaHSO3 ghs05  Danger Warning Corrosive cat. 1 pictogram ghs07  Warning Toxic cat. 4 Irritant cat. 2 or 3 Lower systemic health hazards pictogram
NaHCO3 Non-hazardous
Pentane ghs02  Danger Warning Flammable pictogram ghs08  Danger Warning Systemic health hazards pictogram ghs07  Warning Toxic cat. 4 Irritant cat. 2 or 3 Lower systemic health hazards pictogram ghs09  Warning (for cat. 1) (for cat. 2 no signal word) Environmental hazard pictogram
m-Chloroperbenzoic acid ghs02  Danger Warning Flammable pictogram ghs07  Warning Toxic cat. 4 Irritant cat. 2 or 3 Lower systemic health hazards pictogram
4-tert-Butylcyclohexanone ghs07  Warning Toxic cat. 4 Irritant cat. 2 or 3 Lower systemic health hazards pictogram
4-tert-Butyl-ε-caprolactone ghs07  Warning Toxic cat. 4 Irritant cat. 2 or 3 Lower systemic health hazards pictogram

International Chemical Identifier

The IUPAC InChI key identifiers for the main compounds used in this experiment are provided to facilitate the nomenclature and formulation of chemical compounds and the search for information on the Internet for these compounds.

Diethyl ether RTZKZFJDLAIYFH-UHFFFAOYSA-N
Hexane VLKZOEOYAKHREP-UHFFFAOYSA-N
MgSO4 CSNNHWWHGAXBCP-UHFFFAOYSA-L
NaHSO3 DWAQJAXMDSEUJJ-UHFFFAOYSA-M
NaHCO3 UIIMBOGNXHQVGW-UHFFFAOYSA-M
Pentane OFBQJSOFQDEBGM-UHFFFAOYSA-N
m-Chloroperbenzoic acid NHQDETIJWKXCTC-UHFFFAOYSA-N
4-tert-Butylcyclohexanone YKFKEYKJGVSEIX-UHFFFAOYSA-N
4-tert-Butyl-ε-caprolactone XFKCBMHHCWKGMQ-UHFFFAOYSA-N

References

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