Download Organic Chemistry I - Solved Midterm Exam II | CHEM 3311 and more Exams Organic Chemistry in PDF only on Docsity! Student Name (first, last):
Social Security Number:
TA Name:
CHEMISTRY 3311 (100) Josef Michl
SECOND MIDTERM EXAMINATION October 21, 2004
1. (40 points) Check the correct statements only and make no marks at the incorrect statements:
(%) As wavelength of monochromatic light increases, the energy of its photon decreases.
(.) In NMR spectroscopy a sample is placed in magnetic field and IR light is used to excite vibrations.
(X) The 'H NMR spectrum of ethane contains a single line.
() Under the usual experimental conditions the '\C NMR spectrum of propane contains three lines.
(X) Dimethyl ether and ethanol are constitutional isomers.
(x) 1 g of ethylcyclopropane generates more heat upon complete combustion than 1 g of cyclopentane.
() The twist boat is the most stable conformation of cyclohexane.
(.) At room temperature, cis-1,3-dimethylcyclohexane exists mostly'as the axial,axial conformer.
(X) Trans-1,2-dichlorocyclohexane is chiral.
() The rotation observed for a 5-cm path length ofa 0.01 M aqueous solution of glucose is the same as
the rotation observed for a 10 cm path length of a 0.02 M solution.
(x) A meso compound is not chiral although it contains centers of chirality (stereogenic centers).
() A thermoneutral reaction cannot be exergonic.
() Ina sample that is a 80:20 mixture of enantiomers, the enantiomeric excess is 40%.
(X) A carbene contains a divalent carbon atom.
() The rate ofa thermoneutral reaction with AS! =0 is always the same in forward and reverse directions.
() Sy2 substitution with the cyanide anion proceeds faster in methyl iodide than in ethyl iodide.
(X) Sy] substitution with water proceeds faster in t-butyl iodide than in isopropyl iodide.
(.) Aracemic mixture of enantiomers cannot be resolved into pure enantiomers.
(X) Ethylamine is a weaker acid than ethanol.
(x) Ethylamine is a stronger base than ethanol.
2
2.(20 pts) Write the mechanism of free-radical bromination of isobutane under UV irradiation with
just enough elemental bromine to produce monosubstitution. Show all reaction steps and
structure of the main organic product and ofall intermediates, ifany. Use curved arrows
to indicate how electrons move in the individual elementary reaction steps. Label reaction
steps or groups of reaction steps with names, if they have any.
at = hv _โ
INUTIATION Poa oet โ__โโยป 2(Er-
PROPAGATION Br (cy), โโ> [Br-H 0c (C8)
ee
epee a! โโ
\Brโ Bal
TAMINATION Ae [Bee eb} > if
\Bre (CH), โ? |Br-C(As)s
Compe eV" CCH), โ* CHI, Cโ C (Ct)z
