In this experiment, we alkylate sodium saccharin to N-ethylsaccharin with iodoethane in an aprotic solvent N,N dimethylformamide. Nucleophiles in this experiment will react better in an aprotic solvent. Aprotic solvents have dipoles due to its polar bonds but they do not have H atoms that can be donated into a H-bond. The anions which are the O- and N- of sodium saccharin are not solvated therefore are “naked” and the reaction is not inhibited and preceded in an accelerated rate. The reaction was an SN2 reaction. Since the Oxygen and Nitrogen are more electronegative than the carbon on which they’re attached electrons are pulled towards O- and N- attracting the ethane from Iodoethane. Iodine being more electronegative breaks off from ethane and joins the Na+. Since, the Oxygen of sodium saccharin is more electronegative than the nitrogen therefore this gives oxygen a higher partial negative charge therefore an attack on Oxygen will give a product that is formed faster; this can be called a kinetic product. The transition state energy is lower than a product formation by thermodynamic control. At thermal equilibrium at 80°C a more stable product is form from a higher transitional state energy. The nucleophiles in the molecule sodium saccharin are O- and N- and the major product formed depending on which oh the nucleophile was attacked most in the reaction. Nucleophilic attack by nitrogen will yield N-ethylsaccharin and nucleophilic attach by oxygen will yield O-ethylsaccharin. “N-saccharin is more stable than O- ethylsaccharin because the Ethyl group is attached to the Nitrogen giving the same spacial configuration for the five membered ring (which is flat or planar).” (Richard y.a.). The carbonyl carbon is sp2 and flat. This has little ring strain and is stable. The first bond between carbon and oxygen in a carbonyl group is created by overlapping an sp2 hybrid orbital from carbon with an sp2 hybrid orbital from oxygen (sigma bond). The second...
References: CRC Handbook of Chemistry and Physics, 87th Ed, 2006-2007
Experiment 8 Saccharin
Hunt, Ian. “Chapter 8: Nucleophilic Substitution” Department of Chemistry, University of Calgary. March 8, 2009.
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Merck Index. V13.1. Merck: Whitehouse Station, NJ. 2001
Richard.”N-Ethylsaccharin” March 8, 2009
Saccharin. Wikipedia. March 8, 2009. http://en.wikipedia.org/wiki/saccharin.
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