CHE 230 Exam 1 _Fall 2010 - Department of Chemistry - Illinois ...
CHE 230 Exam 1 _Fall 2010 - Department of Chemistry - Illinois ...
CHE 230 Exam 1 _Fall 2010 - Department of Chemistry - Illinois ...
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10. Determine the formal charge on the BOLD atoms <strong>of</strong> the molecules that are listed below. (20 pts total)-1 +1 -1 011. Consider the cationic molecules methyl cation, CH 3 + and the ammonium cation, NH 4 + . Explain themeaning <strong>of</strong> the positive charge in each case. (30 pts)The methyl cation is a true electrophile at carbon as it is missing electron density and the carbon only hassix electrons associated with it. The nitrogen in the ammonium cation does not possesss the same reactivityas its charge is a result <strong>of</strong> the sharing <strong>of</strong> electron density. There is no vacancy <strong>of</strong> electron density at thenitrogen.12. Identify the following molecules as being either electrophiles (E) or nucleophiles (N) or unreactive (U) atthe central atom. Note: Lone pair electrons are not drawn. If you are concerned about the presence <strong>of</strong> lone pairelectrons, then you should draw the Lewis structure <strong>of</strong> the molecule. (30 pts)SiH 3+BF 4-NH 4+NH 2-H 3 O +AlCl 4-E U U N U U13. Show a reaction between an electrophile and nucleophile from the above molecules in problem 12. (20 pts)© <strong>2010</strong> Pr<strong>of</strong>. S. R. Hitchcock, <strong>Department</strong> <strong>of</strong> <strong>Chemistry</strong>, <strong>Illinois</strong> State University, Normal, IL 61790-41602