Extraction and analysis of two compounds from unknown solution C
Liquid C and solid C were both extracted from unknown solution by first using chemically active liquid-liquid extract, followed by vacuum filtration. Liquid C and solid C were then purified with the use of simple distillation and recrystallization respectively. Through the process of recrystallization, the percentage purity of solid C was found to be 6.01%. The melting point range of purified solid C was 117.0 – 119.0C while the boiling point of liquid C was found to be 117C. The identity of solid C and liquid C was found to be benzoic acid and butyl acetate respectively.
The isolation of individual or groups of compounds can be accomplished with the use of various types of purification techniques. Such techniques include chemically active liquid-liquid extraction and solid-liquid extraction, of which vacuum filtration is used in the case of the latter. Identification of these compounds are established through the methods of infrared (IR) and nuclear magnetic resonance (NMR) spectroscopy as well as the melting and boiling points. Liquid-liquid extraction utilizes the differing solubilities of compounds in solvents that are immiscible. Organic layers, unless chlorinated, will always float on top of aqueous layers. The partition coefficient, K, describes the distribution of compounds in each layer: K = C2/C1. C2 represents the concentration of a certain solute in the second solvent, while C1 represents the concentration of that same solute in the first solvent (Padias). Multiple extractions are implemented in order to extract as much compound as possible.
The use of chemically active extraction, also known as acid-base extraction, is effective in the extraction of compounds from either an aqueous or organic solvent. Conversion into its acid, basic, or neutral counterparts causes a change in its solubility that makes it more accessible for its separation from other solutes (Padias).
In the case of solid-liquid extraction, the separation of compounds is from two different phases – solid and liquid. This can be performed using the techniques of vacuum filtration or hot gravity filtration.
Recrystallization is a technique used to purify solids. It exploits the different solubilities of compounds in different solvents as well as different temperatures (Padias). The solid compound being purified is dissolved in minimal heated solvent, resulting in a hot, concentrated solution. When the concentrated filtrate is allowed to cool down, the solubility of the compound of interest decreases, and as a result begins to form crystals. Impurities that is more soluble than the compound being isolated would remain in solution (Padias).
Simple distillation is a technique used to purify liquid compounds and to separate mixtures of liquids into their individual components based upon their differences in boiling point. This technique includes the vaporization of the liquid of interest in which the vapor is immediately channeled into a condenser, cools, and transitions into a liquid phase (Padias).
The identification of the compounds is done by the analysis of IR and NMR spectroscopy, as well as the determination of melting and boiling points.
In IR spectroscopy, different bonds of molecules absorb different wavelengths of infrared waves, and can bend in one of four different ways – symmetric or asymmetric stretching, or bending in or out of plane (“Introduction to Spectroscopy”). The different movements require different infrared energies, thus different absorption signals are reflected in the resulting IR spectrum. These characteristics allow for the determination of the functional groups present.
In NMR spectroscopy, the nucleus of either 1H or 13C is being observed. When placed in a strong magnetic field, and excited with radio waves, the spin of the nucleus being observed is allowed to decay,...
References: Huston, Ericka, Ryan Weiss, Nicole Kennedy, and George Bandik. Chem 0340 Organic Chemistry II Laboratory Manual. Plymouth: Hayden-McNeil, 2014. Print.
Padias, Anne B. Making the Connections: A How to Guide for Organic Chemistry Lab Techniques. New York: Hayden McNeil, 2007. Print.
"Introduction to Spectroscopy." Chemistry Department. University of Michigan. Web. 20 Sept. 2014. .
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