PS7_2011 - Name Section Rec TA Side 1 of 6 Ch 1b, Problem...

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Unformatted text preview: Name Section Rec TA Side 1 of 6 Ch 1b, Problem Set Seven Due Friday, Feb. 25, 2011 at 4 PM PST in the Drop Box 1. Nucleophiles and electrophiles (16 points) i) State whether the following molecules will react as an electrophile, nucleophile, or both. ii) For the nucleophiles, draw the HOMO. For the electrophiles, draw the LUMO. Name Section Rec TA Side 2 of 6 Ch 1b, Problem Set Seven Due Friday, Feb. 25, 2011 at 4 PM PST in the Drop Box 2. Nucleophile-electrophile reactions (16 points) The molecules shown below are nucleophilic. Identify the nucleophilic atom(s), draw a curved arrow mechanism for the reaction with a generalized electrophile, E+, and provide the corresponding product. Name Section Rec TA Side 3 of 6 Ch 1b, Problem Set Seven Due Friday, Feb. 25, 2011 at 4 PM PST in the Drop Box 3. Curved Arrow Mechanisms (12 points) Complete the mechanisms by drawing the structure of the products in each case. Name Section Rec TA Side 4 of 6 Ch 1b, Problem Set Seven Due Friday, Feb. 25, 2011 at 4 PM PST in the Drop Box 4. Carbonyl reactivity (16 points) Determine which compound in each of the following pairs is expected to be more reactive toward addition of a generalized nucleophile, :Nu, to the carbonyl bond. Explain your reasoning. (a) (b) (c) (d) 2-hexanone or 1,1,1-trifluoro-2-hexanone Acetone or 2,2,4,4-tetramethyl-3-pentanone Cyclobutanone or butanone N,N-dimethylacetamide or 3-methylbutanone Name Section Rec TA Side 5 of 6 Ch 1b, Problem Set Seven Due Friday, Feb. 25, 2011 at 4 PM PST in the Drop Box 5. Carbonyl group structural analysis (16 points) Physical data for carbon monoxide, formaldehyde and acetone is shown in the table below. In this problem, you will use structural analysis to examine the properties of carbon monoxide in relation to other molecules bearing a carbonyl group. Molecule Carbon monoxide Formaldehyde Acetone Bond energy (kcal/mol) 257 166 ~179 Dipole moment (Debyes) 0.11 2.33 2.91 (a) Draw the Lewis dot diagrams for carbon monoxide and formaldehyde. Include any possible resonance structures, and for each molecule, comment on the relative contribution from each resonance structure to the overall molecular structure. (b) Sketch the hybrid orbital structures of carbon dioxide and formaldehyde. How do these structures compare to the Lewis structures drawn in part (a)? (c) Using the structures above, explain why the dipole moment of carbon monoxide is so small compared to other molecules that have carbonyl groups. (d) Using the structures above, explain why the CO bond energy for carbon monoxide is so high compared to other molecules that have carbonyl groups. (e) Based on your reasoning above, do you expect urea, (NH2)2CO, to have a stronger or weaker dipole moment than formaldehyde? Stronger or weaker CO bond energy? Why? Name Section Rec TA Side 6 of 6 Ch 1b, Problem Set Seven Due Friday, Feb. 25, 2011 at 4 PM PST in the Drop Box 6. Acidity of organic molecules (24 points) Sets of related molecules are shown below. Draw the conjugate base of each molecule (include any resonance structures), and within each set, arrange the molecules in order of increasing acidity. Explain your ordering. ...
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This note was uploaded on 03/21/2011 for the course CHEMISTRY 1b taught by Professor Reisman;heath during the Winter '11 term at Caltech.

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