Chemistry 2030 Survey of Organic Chemistry Fall Semester 2013 Dr. Rainer Glaser Examination #1 Bonding, Alkanes, Alkenes & Alkynes Thursday, September 12, 2013, 8:00 8:50 am Question 1. Atomic Structure & Lewis Structures 20 Question 2. Nomenclature of Alkanes, Alkenes & Alkynes 20 Question 3. Conformations of Alkanes 20 Question 4. Reactions of Alkanes 20 Question 5. Reactions of Alkenes & Alkynes 20 Total 100 ALLOWED: Periodic System of the Elements (printed, w/o handwriting on it). Molecular models (you can bring pre-made models). Simple, non-programmable calculator (not really needed). NOT ALLOWED: Books. Notes. Electronic devices of any kind (other than a simple calculator). 1
Question 1. Atomic Structure and Lewis Structures. (20 points) (a) Carbon atom has 6 electrons. Provide the electron configurations of carbon in its ground state. Use the line format (one short line for each AO) to indicate the number of electrons in atomic orbitals 1s, 2s, 2p x, 2p y, and 2p z and indicate the spin (up or down) of the electrons. (3 points) (b) Briefly explain why carbon usually forms 4 bonds and provide the approximate value of the (H C H) angle in methane, CH 4. (3 points) (c) Draw structural formulas for all possible structure isomers with the formula C 3 H 4 Cl 4. (6 points) (d) Draw the three most important resonance forms of carbon dioxide, CO 2. The resonance structures should reflect that the oxygens carry partial (positive, negative) charges. Draw complete Lewis-Kekule structures (all lone pairs, formal charges). Use the correct resonance arrow and the correct brackets. (8 points) 2
Question 2. Nomenclature of Alkanes, Alkenes & Alkynes. (20 points) (a) Draw the abbreviated structural formula of 1,1,1-trichloropropane. Draw all C C and C Cl bonds; you may abbreviate methyl groups as CH 3, methylene groups as CH 2, and so on. (4 points) (b) Draw the line-segment formula of 1-fluorocyclo-1,3-hexadiene. (5 points) (c) Give the IUPAC name of the structure shown. (4 points) (d) Give the IUPAC name of the structure shown. (4 points) (e) Give the IUPAC name of the structure shown. (3 points) 3
Question 3. Conformations of Alkanes. (20 points) (a) Provide a sawhorse drawing of the trans conformation of butane. (4 points) (b) Provide a Newman projection of the trans conformation of butane. (4 points) (c) Provide a Newman projection of the gauche conformation of butane. (4 points) (d) Circle the most stable conformation of the molecule shown. The most stable structure adopts the (chair, boat) conformation and the substituent prefers to be in the (axial, equatorial) position. (8 points) 4
Question 4. Reactions of Alkanes. (20 points) (a) Provide the stoichiometry of the complete combustion of propane to CO 2. (3 points) C 3 H 8 + _._ O 2 _ CO 2 + _ H 2 O (b) Provide the stoichiometry of the incomplete combustion of propane to CO. (3 points) C 3 H 8 + _._ O 2 _ CO + _ H 2 O (c) Provide the structures of the two possible products of monochlorination of 2,3-dimethylbutane. Circle the product that will be formed in the largest amount. (9 points) (d) Provide the structure of the major product of monobromination of 2,3-dimethylbutane. (3 points) 5
Question 5. Reactions of Alkenes and Alkynes. (20 points) (a) Draw abbreviated structures of the substrate and the product of the electrophilic addition reaction of hydrogeniodide (H I) to trans-3-hexene. Provide the product s IUPAC name. (8 points) (b) Provide abbreviated structures (show C C and C Br bonds; do not show C H bonds, write CH, CH 2, CH 3 ) of the two products of the electrophilic addition of H I to 3-methyl-3-hexene. Circle the Markovnikov product, i.e., the one formed in larger amounts. (6 points) (c) Addition of 3 molecules of propene to borane, BH 3, forms tri-n-propylborane, B(CH 2 CH 2 CH 3 ) 3. Workup of tri-n-propylborane with an alkaline solution of (give formula of hydrogenperoxide) affords (1-propanol, 2-propanol, or 3-propanol). The alcohol formed in this hydroboration / oxidation sequence is the (Markovnikov, anti-markovnikov) product. (3 points) (d) The Pt-catalyzed heterogeneous hydrogenation of 2-hexyne initially forms (provide the name of the intermediate alkene). The intermediate alkene will be a (cis, trans) alkene. The intermediate alkene then adds more hydrogen gas (H 2 ) to form. (3 points) 6