A Breathalyzer makes use of the fact that alcohols (in this case ethanol) oxidize into carboxylic acids. It uses the strong oxidizing agent Potassium dichromate in a yellow solution of sulfuric acid, under the presence of a Silver Nitrate catalyst, to complete the reaction quickly. As ethanol oxidizes and the Potassium dichromate reacts, the chromate ion changes from Cr (VI) to Cr (III). This causes the color intensity of the yellow solution to decrease, and a spectrophotometer in the breathalyzer compares the absorbance of this solution with that of an unreacted solution
Using Beer’s law, the spectrophotometer can relate concentration to absorbance levels of the chromium ion. The amount of alcohol present is proportional to the stoichiometric coefficients. An actual breathalyzer only needs to detect 25 micrograms of ethanol to give a reading 0.10 Blood Alcohol Level.
The main protocol for the synthesis of β-alkoxy alcohols is the alcoholysis of 1,2-epoxides. To synthesize epoxides, we can use oxone in the presence of transition metal complexes, or cyclodextrines, or via the formation of dioxiranes.
An application of this type of reaction is the synthesis of β-methoxy alcohols. It is done by the one-pot reaction of alkenes with oxone in methanol without any other catalyst.
Note: Oxone (2KHSO5·KHSO4·K2SO4) is the registered trademark from Du Pont.
General reaction and some examples are shown above.
The picture above shows a few of the steps in the creation of amphetamines. In these steps, tosyl chloride is added to (2,5-dimethoxyl-4-methylphenyl)-2-propanol to create the tosylate. After this step, the reaction can proceed in one of two ways. If the chirality of the amphetamine is not important, ammonia is added to the tosylate to give 2,5-dimethoxy-4-methylamphetamine. This reaction has an 80% yield, but has a racemic mixture of products because it is thought to be an SN1 reaction. If the chirality is important, the tosylate is converted into an azide with sodium azide, then hydrogenated using a paladium catalyst to form 2,5-dimethoxy-4-methylamphetamine. Forming the amphetamine using this method gives a final yield of about 77%. The chirality of the original alcohol is inverted by the tosylation, so reacting an (S)-alcohol with the tosyl-azide-hydrogen sequence would give an (R)-amphetamine, and vice versa.
