Identify alcohol

Sodium metal test

Chemical properties

Alcohols react with active metals like sodium and liberate hydrogen gas that can be observed in the form of effervescence

http://amrita.olabs.edu.in/?sub=73&brch=8&sim=141&cnt=1

http://documents.mx/documents/experiment-8b.html

Physical Properties

The metal melts below the boiling point of water (97^oC). In its elemental state it has been used as a molten coolant in nuclear reactors and is currently under research for sodium/sulfur batteries. Its most common compounds for industrial use include sodium chloride, sodium hydroxide (lye), sodium carbonate (washing soda) and sodium sulfate.

Color	Silver
Phase at Room Temperature	Solid
Density	0.968 g/cm3
Boiling Point	883o C
Melting Point	97.72o C

Complications

Combined with active hydrogen. This test gives a positive answer

Ceric ammonium nitrate test

Chemical properties

Alcohols reacts with ceric ammonium nitrate to form a red coloured alkoxy cerium (IV) compound

http://amrita.olabs.edu.in/?sub=73&brch=8&sim=141&cnt=1

Physical properties

Complications

Hot solutions of Ce(IV) oxidize many organic compounds

http://884131013.blogfa.com/post/9

The Chromic Acid Test

Chemical properties

Mechanism of the Jones Oxidation

The is a mixture of chromic trioxide or sodium dichromate in diluted sulfuric acid, which forms chromic acid in situ

The alcohol and chromic acid form a chromate ester that either reacts intramolecularly or intermolecularly in the presence of a base (water) to yield the corresponding carbonyl compound

http://www.organic-chemistry.org/namedreactions/jones-oxidation.shtm

Shows positive test for

1^o and 2^o alcohols and aldehydes

Reactions:

aldehydes and primary alcohols are oxidized to carboxylic acids while the Cr⁺⁶ ion in the chromic acid is reduced to Cr⁺³.

secondary alcohols are oxidized to ketones while the Cr⁺⁶ ion in the chromic acid is reduced to Cr⁺³.

Physical properties

Complications

• Enols may give a positive test
• Phenols give a dark colored solution which is not blue-green like a positive test

http://academics.wellesley.edu/Chemistry/chem211lab/Orgo_Lab_Manual/Appendix/ClassificationTests/alcohol.html

The Lucas Test

Chemical properties

The Lucas test tells whether an alcohol is primary, secondary or tertiary. Tests like this were once regularly used to determine the structure of molecules. But modern structure elucidation methods like NMR have made such tests obsolete. What is the Lucas test? It’s just the S_N1 reaction of an alcohol with HCl. The Lucas reagent is ZnCl₂ in concentrated HCl.

SN1 reaction of an alcohol with HCl

Recall that in S_N1 reactions, a carbocation is formed. So alcohols that form stable carbocations will react faster than alcohols that form less stable carbocations. The product of this reaction is an alkyl chloride, which is insoluble in water; it’s formation will turn the solution cloudy. The rate with which a solution turns cloudy tells you whether the alcohol was 1º, 2 º, or 3. Tertiary alcohols will react and turn cloudy right away. Secondary alcohols will take a few minutes to react, and primary alcohols will won’t react at all.

3° carbocations are more stable than 2° or 1° carbocations and so form faster.

Based on this theory, you can expect the 2-methyl-2-propanol (also know as tert-butanol) to react faster than 2-butanol (also known as sec-butanol). 1-Butanol won’t react at all.

You might be wondering how the zinc gets involved in this reaction. Zinc is a Lewis acid, and so can accept a lone pair on an oxygen atom, resulting in a positively charged oxygen, which then acts a leaving group, leaving behind a carbocation. This is similar to what happens when oxygen picks up a proton, but happens even faster when zinc is present. So zinc speeds up the formation of the carbocation, which increases the rate of reaction. The Lucas test will go faster with ZnCl₂ than in its absence.

Zinc is a Lewis acid, and so speeds up the formation of the carbocation.

http://www.mendelset.com/articles/693/properties_alcohols

A mixture of anhydrous ZnCl₂ + conc. HCl is called as Lucas reagent.

Primary	ppt. appears after heating
Secondary	ppt. appears with in 5 minutes
Tertiary	ppt. appears immediately

Physical properties

Complications

The test applies only to those alcohols soluble in the reagent (monofunctional alcohols lower than hexyl and some polyfunctional alcohols.) This often means that alcohols with more than six carbon atoms caot be tested.