Chemistry 230–002 First ExaminationSeptember 23, 2003Name (please PRINT LEGIBLY) (last) (first)Problem Score1. (a-e) /282. (a-c) /143. (a-b) /164. (a-f) /245. (a-c) /18Total /100Please, please, PLEASE observe the following.1) Write LARGE and LEGIBLY. If I can’t read what you write, I can’t give you full or partialcredit.2) Read each question carefully before answering. If you don’t answer the question I posed,you won’t get credit.3) For questions with multiple parts, be consistent. Your answer to a later part will be gradedbased on the earlier part being correct, whether or not it actually is. For example, suppose Iasked the following questions:(a) What is the hybridization of the C atom in methane? (5 pts)(b) What is the H–C–H bond angle? (5 pts)Three students gave the following answers:Student 1 Student 2Student 3(a) sp2sp2sp3(b) 120° 109° 109°Score: 0 pts + 5 pts 0 pts + 0 pts 5 pts + 5 ptsStudent 1 correctly answered (b) given her answer for (a). Student 2 incorrectly answered (b)given his answer for (a), even though (b) is formally correct. Student 3 correctly answered both (a)and (b) and got full credit for the question.2(1) (28 pts. total.) Methyl isocyanate, a compound that killed thousands and blinded tens ofthousands of people in Bhopal, India, in 1984, has the formula C2H3NO.(a) (4 pts.) How many total valence electrons does methyl isocyanate have?(b) (6 pts.) The σ-bond network (atom-to-atom connectivity) of methyl isocyanate is sketchedbelow. Fill in the remainder of electrons to draw the BEST resonance structure for methylisocyanate. Include all unshared pairs of electrons and any formal charges.NCOCHHH(c) (6 pts.) What are the hybridizations of:1. the terminal C atom? 2. the N atom? 3. the internal C atom? (d) (4 pts.) What are the bond angles about:1. the N atom? 2. the internal C atom?3(e) (8 pts.) Draw a diagram showing all of the atomic orbitals in CH3N=C=O. Indicate whichatomic orbitals overlap to form σ bonds, which ones overlap to form π bonds, and which oneshold unshared electrons. I’ve drawn out the orbitals around O to get you started. (Note: Forsake of clarity, please don’t draw the small back lobes of the hybrid orbitals.)CHNHHCOsp2sp2sp2p+p–σ4(2) (14 pts. total.) Consider the vinyl cation, whose structure is shown below.H2CCH(a) (5 pts.) What is the hybridization of the electron-deficient carbon in the vinyl cation?(b) (4 pts.) Based on your answer to (a), what are the ideal bond angles about the electron-deficient carbon in the vinyl cation?(c) (5 pts.) The phenyl cation, shown below, is much higher in energy than the vinyl cation.Why? (Think about the optimum bond angles about the electron-deficient carbon.)HHHHH5(3) (16 pts. total.) Consider the compound with the formula C5H8F2. A compound with thisformula has either one ring or one π bond.(a) (8 pts.) Draw two skeletal isomers of C5H8F2. (There are many correct answers.)(b) (8 pts.) Draw two stereoisomers of C5H8F2. (There are many correct answers.)6(4) (4 pts. each, 24 pts. total.) For each pair of compounds, indicate the relationship of the firstcompound to the second by circling the correct answer.(a)is a skeletal isomer ofis a configurational diastereomer ofis a conformational diastereomer ofis an enantiomer ofis a resonance structure ofis the same compound ashas none of the above relationships toOOOO–(b)is a skeletal isomer ofis a configurational diastereomer ofis a conformational diastereomer ofis an enantiomer ofis a resonance structure ofis the same compound ashas none of the above relationships toOHOH(c)BrHHHCH3HBrCH3HHHHis a skeletal isomer ofis a configurational diastereomer ofis a conformational diastereomer ofis an enantiomer ofis a resonance structure ofis the same compound ashas none of the above relationships to7(d)is a skeletal isomer ofis a configurational diastereomer ofis a conformational diastereomer ofis an enantiomer ofis a resonance structure ofis the same compound ashas none of the above relationships toOOH3CCH3(e)is a skeletal isomer ofis a configurational diastereomer ofis a conformational diastereomer ofis an enantiomer ofis a resonance structure ofis the same compound ashas none of the above relationships toOO(f)is a skeletal isomer ofis a configurational diastereomer ofis a conformational diastereomer ofis an enantiomer ofis a resonance structure ofis the same compound ashas none of the above relationships toHHHH8(5) (6 pts. each, 18 pts. total.) Using the curved arrow formalism, draw the best resonancestructure of each of the following
View Full Document
Unlocking...