Name:
ORGANIC CHEMISTRY I (CHEM 323)
EXAM 1
September 19, 2013
There are six pages, TEN questions, and a total of 110 points in this exam, which gives an extra 10 points on top of that required for a “perfect” paper. Please read each question carefully and possibly more than once. Good luck…
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1.What is the total charge of the compound below?
1.1.Write the structure of the missing resonance structure below, making sure that the “octet rule” is satisfied for all the atoms (other than hydrogen )and the carbon nolonger has a lone pair. Use curly arrows to show electron movements.
1.2.What property of the compound above is emphasized by your ability to write a resonance structure for it?
electron delocalization
1.3.Write the structure of an acid for which the compound above is the conjugate base.
(although you can strictly write two different structures for the acid, please write the structure which is much more stable)
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2.Complete the reactions below and identify the structures of the missing products. Use curly arrowsto show electron transfers, bond formations, and/or bond cleavages. Show all formal charges (if any).
Questionsubmitted by Bethany
2.1.
Inspired by questionfromSheryl
2.2.
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3.Circle the best correct answer (only ONE) for each of the multiple choice questions given below:
3.1.Which one of the compounds below has a heteroatom with a formal charge of +1?
3.2.Which of the following is the correct structure for tert-butylcyclopentane?
3.3.Which of the following is an amine?
3.4.The electron configurations for atoms A, B, and C are given below. Which of the atoms listed is/are the least likely to make a bond with another one identical to itself?
(A) 1s1(B) 1s22s22p6(C) 1s22s22p2
(1) only A(2) only B (3) only C (4) both A and B (5) both A and C
3.5.Place the conjugate bases below in order of strength (strongest base first, weakest base last)
(1) A>B>C(2) B>A>C(3) C>A>B(4) A>C>B(5) C>B>A
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4.Draw (a) a “zig-zag” structure and (b) give the molecular formula
for the alkane, whose Newman projection representation is given below.
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5.In the box under the structure given below write the number of signals detected in the C-13 NMR spectrum.
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6.Cyclohexane templates in chair form are given below. Place substituents in appropriate positions for each pair to construct dimethylcyclohexane structures as indicated. The relationship for each pair is specified.
6.1.Same carbon connectivity; different spatial arrangements; two structures are
inter-convertible
6.2.Same carbon connectivity; different spatial arrangements; two structures are
not inter-convertible (also different physical properties)
Question submitted by Jamie
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7.Draw the Newman Projection Representations for gauche and anti-staggered conformations of ethylene glycol (structure given below).
Indicate which is which.
7.1.Surprisingly the gauche conformation is more stable. Explain why.
(You might wish to sketch the interactions involved –as well as a narrative explanation).
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8.Name the following moleculeaccording to the IUPAC rules of naming
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9.In the illustration of acetaldehyde (C2H4O) shown below name each of the two orbitals, whose overlap forms the bond indicated by an arrow.
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10.Each of the following multiple-choice questions is associated with a correct explanation. You need to circle the correct answer for both parts of the question.
10.1.In which of acid-base reactions below (1 or 2) the products on the right-hand-side of the equation are favored?
Correct Reasoning:
(1)The conjugate acid formed is weaker thus more stable than the acid on the left-hand-side of the equation.
(2)The conjugate acid formed is stronger thus more stable than the acid on the left-hand-side of the equation.
(3)The conjugate base formed is stronger; thus the acid on the left-hand-side of the equation must also be stronger.
(4)An alcohol is more stable than an amine.
10.2.Which one of the molecules below is the most volatile?
Correct Reasoning:
(1)Contains fewer carbon atoms
(2)Smaller surface area
(3)Stronger inter-molecular forces
(4)Weaker van der Waals forces
(5)Both (2) and (4)
10.3.Which of the following bonds, described as orbital overlaps, is likely to be broken most easily?
(1) sp3-sp3 ()(2) p-p ()(2) sp2-p
Correct Reasoning:
(1)face-to-face overlaps form -bonds.
(2)-bonds are easily broken.
(3)overlap is less extensive for a sideways overlap.
(4)when a carbon molecule forms a double bond, it utilizes sp2 bonds.
10.4.The C-13 NMR spectrum of 2-bromobutane is given below:
The signal appearing at 53 ppm can be attributed to which carbon?
Correct Reasoning:
(1)high electron density shields the carbon nucleus from the external magnetic field and thus causes resonance at low field (53 ppm).
(2)primary carbon signals are observed in the 40-60 ppm region
(3)bonding to a halogen increases the electron density of the carbon
(4)bonding to an electronegative atom reduces the magnetic effect of the electrons on the carbon nucleus
10.5.The mass of 1 mole of water is 18 g. What is the volume of 1 mole of water in the
gas phase at 1 atm of pressure?
(1)18 mL (2) less than 18 mL (3) more than 22,000 mL (4) 1 cubicinch
Correct Reasoning:
(1)The volume of 1.0 g of water is 1.0 mL
(2) There are more molecules in a mole of water when it is in the gas phase
(3) The volume of 1 mole of any gas is 1.0 cubic inch
(4)The molecules are much further apart in the gas phase compared to liquid or solid phases
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