Chemistry 2030 Survey of Organic Chemistry Fall Semester 2014 Dr. Rainer Glaser

Transcription

1 Chemistry 2030 Survey of Organic Chemistry Fall Semester 2014 Dr. Rainer Glaser Examination #1 Bonding, Alkanes, Alkenes & Alkynes Thursday, September 18, 2014, 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 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

2 Question 1. Atomic Structure and Lewis Structures. (20 points) (a) Fluorine atom has 9 electrons. Provide the electron configurations of fluorine 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) Provide the approximate value of the (H O H) angle in water, H 2 O, and state the hybridization at O in water. (3 points) (c) Draw structural formulas for all possible structure isomers with the formula C 4 H 9 F. Consider fluoro derivatives of normal butane and also of isobutane. (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

3 Question 2. Nomenclature of Alkanes, Alkenes & Alkynes. (20 points) (a) Draw the abbreviated structural formula of 1,2,3-trifluoropentane. Draw all C C and C F bonds; you may abbreviate methyl groups as CH 3, methylene groups as CH 2, and so on. (b) Draw the line-segment formula of 1,3-cycloheptadiene. (c) Give the IUPAC name of the structure shown. (d) Give the IUPAC name of the structure shown. (e) Give the IUPAC name of the structure shown. 3

4 Question 3. Conformations of Alkanes. (20 points) (a) Provide a sawhorse drawing of the gauche conformation of butane. (b) Provide a Newman projection of the gauche conformation of butane. (c) Provide a Newman projection of the trans conformation of 1,2-dichloroethane. (d) Several conformations are shown of 1,4-dibromocyclohexane. For each structure, write next to it whether it is chair or a boat conformation, and write next to every bromine atom whether it is in an axial (ax) or equatorial (eq) position. Circle the most stable conformation of the molecule shown. (8 points) 4

5 Question 4. Reactions of Alkanes. (20 points) (a) Provide the stoichiometry of the complete combustion of hexane to CO 2. (3 points) 2 C 6 H 14 + _ O 2 _ CO 2 + _ H 2 O (b) Provide the stoichiometry of the incomplete combustion of cyclohexane to CO. (3 points) C 6 H 12 + _ O 2 _ CO + _ H 2 O (c) Provide the structures of the two possible products of monochlorination of 2-methylpropane. 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-methylpropane. (3 points) 5

6 Question 5. Reactions of Alkenes. (20 points) (a) Draw complete structures (show all atoms) of the substrate and of the product of the addition reaction of bromine (Br 2 ) to 1-butene. Provide the product s IUPAC name. (b) Draw complete structures (show all atoms) of the substrate and of the one product of the addition reaction of hydrogeniodide (H I) to 2,3-dimethyl-2-butene. Provide the product s IUPAC name. (6 points) (c) Provide complete structures (show all atoms) of the two possible products of the electrophilic addition of H I to 2-methyl-2-butene. Circle the Markovnikov product, i.e., the one formed in larger amounts. (6 points) (d) Electrophilic addition reactions of H X to alkenes proceed in (one, two, three) reaction steps and involve (one, two, three) transition states and (one, two, three) short-lived intermediates. In the first reaction step, a proton is added to the alkene s double bond and a (radical, carbocation, carbanion) is generated. 6