The Jones Reaction: The Oxidation Of Borneol To Camphor
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Introduction
Reduction/Oxidation (Redox) reactions are ones that change the oxidation state of a compound. The oxidation state refers to the acquired charge (gained or lost electrons) of an element in relation to its original charge (i.e. S + 2e- пє S2+); in a compound, the overall oxidation state is calculated by adding all the charges of the elements present. The addition of electrons makes the element “reduced” and the loss of electrons is called “oxidized”. These reactions can be carried out in lab, or they can occur naturally via oxidants or reductants—substances that have the ability to oxidize or reduce other substances, respectively.
Theory, Reactions, and Mechanisms
In this lab, Borneol will be oxidized to camphor in a common reaction known as the Jones Oxidation Reaction. It is true that oxidation reactions subtract electrons, lowering its oxidation state. However in organic chemistry, a more detailed explanation of the oxidation reaction is appropriate for a better understanding; organic oxidation reactions are ones in which:
Oxygen is inserted into a bond
Hydrogen is lost across a bond
Carbon or hydrogen is replaced by a more electronegative element
There are several general reactions, and several reagents that catalyze the reaction according to the functional group it works on. For primary alcohols, several reagents can be used:
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The Jones reagent (CrO3/H+, Cr2O72-/H+, H2CrO4),
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Potassium permanganate (KMnO4/-OH or H+),
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Collins reagent (CrO2/Pyridine “PCC” (no water present)
Secondary alcohols use the same reagents as primary alcohols.
Tertiary alcohols are resistant to oxidation.
For the aldehydes, the Tollins reagent (Ag(NH3)2 is used in addition to the potassium permanganate and the Jones reagent.
Scheme:
Reagent Table and Instruments
Common Name
Molecular Formula
Molecular Weight (g/mol)
Important Properties
Borneol
C10H18O
154.25
Easily oxidized to the ketone that yields camphor; melting point 208 ÐoC
Camphor
C10H16O
152.23
Can work medicinal as a local anesthetic or antimicrobial agent; melting point 179.75 ÐoC
Sodium Dichromate
Na2Cr2O7 2H2O
298.00
Very harmful to the skin; can cause cancer; melting point 357.00 ÐoC
Diethyl Ether
C4H10O
74.12
Light, colorless, highly flammable; partially soluble in water; melting temp в?116.3 ÐoC
Magnesium Sulfate
MgSO4
120.41
Also known as Epsom salt, commonly used as a bath salt; melting point 1124ÐoC
Sulfuric Acid
H2SO4
10 ÐoC
Very soluble in water (when added to it), burns a lot; melting point 10 ÐoC
Apparatus Setup
Procedure
The first step taken in this lab was the preparation of the Jones reagent: 2.0g of sodium dichromate was dissolved in 6mL of water in a 250mL Erlenmeyer flask. 2mL of sulfuric acid was added to the solution. Caution was taken to add the acid slow, as much heat is generated. An additional 6mL of water was added to dilute the solution, and then it was placed in a 50mL Erlenmeyer flask and cooled on an ice bath.
1.0g of d,l-borneol was