Identification of Alcohols and Phenols

Identification of Alcohols and Phenols

Abstract

Specific groups of atoms in an organic molecule determine its physical and chemical properties. These groups are called functional groups. Functional groups are responsible for the characteristic reactions of a particular compound. This experiment will deal with organic compounds with the functional groups (-OH) which are alcohols and phenols. The objectives of the experiment is to examine and differentiate the physical and chemical properties of alcohols and phenols. The samples were 1-butanol, 2-butanol, 2-methy-2-propanol, phenol and an unknown that was tested for solubility in water and acidity test to determine its physical properties. For the determination of chemical properties, the Iodoform, Lucas, Chromic acid and Iron (III) Chloride was performed on each sample. The unknown was soluble in water similar to the alcohol samples with a ph~ 4-5. The unknown tested positive for the Lucas and Chromic Acid just like the alcohols but more similarly like the 2-butanol. It was concluded that the unknown is a secondary alcohol.

Keywords:        Alcohols, Phenols, Lucas, Iron (III) Chloride, Iodoform, Chromic Acid.

Introduction

        Functional groups are group of atoms responsible for the characteristic reactions of a particular compound. This experiment dealt with organic compounds which contain the functional group (-OH) which are alcohols and phenols.

        Alcohols are important commercially and include uses as solvents, drugs and disinfectants. It can also be classified as either a primary (°), secondary (2°) or tertiary (3°).[pic 2][pic 1]

        Phenols bear a close resemblance to alcohols structurally since the hydroxyl group is present though the (-OH) group in phenols are connected to a carbon that is part of an aromatic ring which makes the chemistry much more different. Phenols are more acidic than alcohols, concentrated amounts of the solutions are toxic and can cause severe skin burns.

Physical Properties of Alcohols and Phenols:

1. Polar Compounds

-because of the hydroxyl group present

-ability to form hydrogen bonds

1. Soluble in Water
2. Soluble in Many Organic Solvents

Chemical Properties of Alcohols and Phenols’ Tests:

1. Lucas Test

- a mixture of Zinc Chloride in hydrochloric acid.

-used to distinguish between primary, secondary and tertiary alcohols

- Tertiary alcohols react rapidly and gives an insoluble white layer[pic 3]

- Secondary alcohols react slowly and after heating slightly gives the insoluble white layer

- Primary alcohols do not react

-Any formation of a heterogeneous phase or emulsion is a positive test.

1. Chromic Acid Test

-use to distinguish primary and secondary alcohols from tertiary alcohols

-using acidified dichromate solution, primary alcohols are oxidized to carboxylic acids, secondary alcohols are oxidized to ketones and tertiary alcohols does not react with the chromic acid.[pic 4]

1. Iodoform Test

-only alcohols with part structure CH3CH(OH) will react

-these alcohols will react with Iodine in aqueous solution of NaOH to give the yellow precipitate Iodoform.

1. Acidity of Phenol

-Phenol is a carbolic acid. Phenol will react with base, thus phenols readily dissolve in base solutions.

1. Iron (III) Chloride

-Addition of aqueous Iron (III) Chloride to a phenol gives a colored solution. Depending on the structure of the phenol, the color can vary from green to purple.

        The objectives of the experiment is to 1. Examine the physical and chemical properties of representative alcohols and phenols; 2.Compare differences in chemical behavior between alcohols and phenols and last, use the information obtained from the experiment to identify the unknown.

Methodology

Physical Properties of Alcohols and Phenols

        The test compounds 1-butanol, 2-butanol, 2-methyl-2-propanol, and an unknown were labeled as A, B, C, and D respectively. In separate test tubes, ten drops of each sample were put separately and was diluted with distilled water (3mL). Next, the pH of the samples’ aqueous solutions was tested by transferring a drop of liquid onto the pH paper. The observations were recorded.

Chemical Properties of Alcohols and Phenols

        The test compounds 1-butanol, 2-butanol, 2-methyl-2-propanol, and an unknown were labeled as A, B, C, and D respectively.

1. Iodoform test.

Five drops of each sample were placed into separates test tubes, water (5mL) and the samples that were insoluble was water bathed. Then drops of NaOH was added, was warmed in water bath at 60°C and I2-KI solution was added, and shaken until brown. More than drops were added yet no brown color appeared and no light yellow precipitate was produced.

1. Lucas Test

Five drops of each sample were placed into separate test tubes, the Lucas reagent was added (1mL), was mixed well by tapping the test tubes lightly for a few seconds and was let to stand for 5 minutes.

1. Chromic Acid Test

Five drops of each sample were placed into separates test tubes, ten drops of acetone and two drops of chromic acid were added, was water bathed and any color changes was noted.

1. Iron (III) Chloride Test

Five drops of each sample were placed into separates test tubes, two drops of FeCl3 were added to each test tube, was observed and data was recorded.

From the results and observations, the unknown was identified.

Results and Observations

1. Physical Properties of Alcohols and Phenols

1. Chemical Properties of Aldehydes and Ketones