Determination of Unknown Liquid (2-Butanol)

Topics: Alcohol, Distillation, Solubility Pages: 10 (2586 words) Published: October 12, 2010
-1Determination of an Unknown Liquid (2-butanol) Through Fundamental Analysis

Lee Billips
Department of Chemistry, Shippensburg University, 1871 Old Main Drive. Shippensburg, PA, 17257.

Abstract: The identification and characterization of unknowns are an important part of organic chemistry. It is fundamental to know experimental methods to deductively identify compounds (1) . The determination of unknown #6 (2-butanol) was identified by a series of test; first taking the boiling point (94-96 C), performing a solubility test, Beilstien test, Ignition test, and the appropriate functional group tests. An infrared spectrum and an NMR spectrum were then obtained and confirmation of the compound was proved.

2-butanol (sec-butyl alcohol)

Introduction: The determination of unknowns is an important skill to organic chemist that involves choosing of appropriate tests, analysis/observation, and deductive reasoning to precisely categorize and identify the compound. The physical description is essential to observe to get an idea of what substance you are working with (state, color, and odor). In this case all unknowns were liquids, but throughout testing if a chemical reaction occurs with your unknown it is necessary to compare its properties to its original stature. Prior to any testing the unknown sample should be purified through some form of distillation to ensure accuracy and precision. Distillation is the process of vaporizing a liquid, condensing the vapor, and collecting the condensate in another container(2) . The technique is useful in separating liquid components that have different boiling points (impurities). The boiling point is also an important characteristic of a liquid that should be recorded. (2)The boiling point is the temperature at which the vapor pressure of the liquid equals the environmental pressure surrounding the liquid (inverted capillary test). A solubility test on the unknown liquid was another fundamental part of the analysis. Solubility is the ability for the solute (unknown) to be dissolved in a liquid solvent to form a homogeneous solution. Using 5%HCl, 5%, NaHCO3, 5%NaOH, concentrated H2S04, and water, as solvents, it was possible to determine the main functional group of the compound. When the main functional group is established specific tests can be performed to determine the location of the functional group (primary, secondary, tertiary). An IR spectrum was taken to reassure the correct functional group was identified. Infrared spectroscopy is the subset of spectroscopy that deals with the infrared region of the electromagnetic spectrum(2) . From this spectrum the peaks show the functional groups within the compound. Nuclear magnetic resonance spectroscopy was also used to determine the exact structure of the compound. NMR exploits nuclear spins at fine frequencies to identify specific location of each atom(2) . In essence, it is this spectrum that proved the location of the functional group (primary, secondary, tertiary).

Experimental Procedure:

5x small test tubes 3-Neck Distillation Head Hot Plate NMR
Pipet bulb 5mL Conical vial Thermometer Adapter 3mL conical vial
Copper wire 10mL Round Bottom Flask Stirring Bar
Water condenser 10mL Graduated Cylinder Infrared Spectrum

5% HCl Concentrated H2S04 95% ethanol Acetone 3,5-dinitrobenzoyl chloride
5% NaHCO3 Water Cerium(IV) Chromic acid
5% NaOH KMNO4 Lucas Reagent 1,2 dimethoxymethane
-Solvents purchased by Fisher Scientific and glassware can be obtained in standard organic lab kit.

Safety- Avoid contact with eyes and skin, reagents are irritants. Concentrated H2SO4 is toxic...
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