CHEM 233, Spring 2016
Midterm #1
Ian R. Gould
COMPLETE THIS SECTION : Up to TWO POINTS will be removed for incorrect/missing information!
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PRINTED FIRST NAME
PRINTED LAST NAME
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ASU or Posting ID
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Extra Credit_____/5
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• WRITE CLEARLY!
• MOLECULAR MODELS ARE ALLOWED
H
He
Li Be
B
Na Mg
K
Total (incl Extra)________/175+5
Ca
Sc Ti V
Cr Mn Fe Co Ni Cu Zn
Rb Sr
Y
Cs Ba
Lu Hf Ta W
Zr Nb Mo Tc Ru Rh Pd Ag Cd
Re Os Ir Pt Au Hg
small range
range of values
broad peak
C
N
O
F
Ne
Al Si P
S
Cl
Ar
Ga Ge As Se Br
Kr
In Sn Sb Te I
Xe
Tl Pb Bi Po At
Rn
O H
C N
N H
C O
C
C
H
2720–2820
2 peaks
C
O
N
C
H
O
C O H
R
R
3500
O
CH
2200
C
R C OH
(δ, ppm)
11
220
10
200
9
180
8
160
6
120
R C
C
R2C
Aromatic
C
1650 1500
NR2
O
C CH3
–H2C NR2
7
140
O
X
–H2C
C CH2
O
R C OH
O
1710
NMR Correlation Charts
Aromatic Ar H
mainly 8 - 6.5
H
1600
2000
2500
–OCH2–
NH2 variable and condition dependent,
ca. 2 - 6 δ
OH
O
1680
C
3000
O
OR
1735
C
broad ~3000
(cm-1)
N
O
2200
2850–2960
broad ~3300
1600–1660
C
C
broad with spikes ~3300
O H
C
C
H
H
3000–
3100
N H
Infrared Correlation Chart
usually
strong
O
C H
3300
Interaction Energies, kcal/mol
Gauche
Eclipsing
~1.0
~0.9
H/H
Me/Me
~1.4
~0.95
H/Me
Et/Me
Me/Me ~2.6
i-Pr/Me ~1.1
Me/Et ~2.9
t-Bu/Me ~2.7
CR2
5
100
N
4
80
RC
C CH
3
60
–OCH2–
CR
Alkyl
3° > 2° > 1°
2
40
C
C NR2
1
20
Alkyl
X
3° > 2° > 1°
0
0
-2-
CHEMISTRY 233, Fall 2016, MIDTERM #1
NAME
Question 1 (12 pts.) Circle and identify all functional groups in the following structure, ignore alkyl
groups. Indicate any amines, amides or alcohols as primary, secondary or tertiary, as appropriate.
2° amine
HN
aromatic
N
N
3° amine
3° amine
O
F
halide
O
ketone
Ciprofloxacin, the only drug
specifically approved by the FDA
for treatment of inhalation
anthrax exposure
carboxylic
acid
OH
Question 2 (22 pts.) Rank the pairs of electrons indicated, A, B, C and D in order of increasing
energy. Give an explanation for your choice, most of the points are for the explanation, not the
order.
B (σ-bonding)
A (non-bonding)
B < D < A < C
H
O
C
(non-bonding)
highest
energy
lowest
energy
P
H
D (π-bonding)
non-bonding electrons are higher in energy than bonding electrons, therefore A and C are highest
in energy, phosphorus is larger and less electronegative than oxygen, C are thus highest
π-bonding electrons are higher in energy than σ-bonding electrons, thus D is next highest and B is
lowest
Question 3 (24 pts.) For the structures A and B below:
a) Indicate (in words, do not draw on the structures) the largest BOND DIPOLE moment(s) in each
the largest bond dipole moment in A is that associated with the C-N triple bonds
the largest dipole moment in B is that associated with the C-F bond
b) Between these two largest bond dipole moments (the one from A and the one from B), which
would be larger? Give a brief explanation.
A has a larger MOLECULAR dipole moment because it has two larger bond dipole
moments that add in (roughly) the same direction as the two smaller bond dipole moments
in B
c) Draw the MOLECULAR DIPOLE MOMENTS ON TOP OF THE STRUCTURES. Your drawings
do not need to illustrate the size of the dipole, only the direction. If there is no molecular dipole,
indicate so. BRIEFLY explain which structure would have the larger MOLECULAR dipole moment.
N
C
A
C
N
Br
F
B
the C-N triple bond dipole moment is larger because even though F is more electronegative than N,
the electrons in the pi-bonds in the triple bond are highly polarizable
CHEMISTRY 233, Fall 2016, MIDTERM #1
NAME
-3-
Question 4 (40 pts.) For the molecular formula C4H8O
a) Give the degrees of unsaturation 1 degree of unsaturation
b) Draw SEVEN structural isomers that obey the normal rules of valence for each atom. Include all
non-bonding electrons. You can draw Lewis structures or line-angle structures (your choice). If you
draw line-angle structures, don't forget to include the H atoms that are normally included as part of
the functional groups.
O H
O
O
O
H
O
O
O
O
H
O
H
O
O
O
O
O
H
H
H
O
H
H
H
O
O
O
O
here are a few......
O
H
c) Draw TWO PAIRS of stereoisomers that obey the normal rules of valence for each atom. Include
all non-bonding electrons. If you draw line-angle structures, don't forget to include the H atoms that
are normally included as part of the functional groups.
DO NOT INCLUDE ANY STRUCTURES in part c) THAT WERE DRAWN AS PART OF
YOUR ANSWER TO PART b) OF THIS QUESTION
O
H
O
+
O
+
O
H
here are four pairs
O
H
+
O
H
O
H
+
O
Extra Credit (5 pts.) BRIEFLY give ONE way in which anti-bonding orbitals are used by
organic molecules
they accept electrons in chemical reactions AND they are where the electrons "go to" upon
photochemical excitation
H
CHEMISTRY 233, Fall 2016, MIDTERM #1
-4-
NAME
Question 5 (30 pts.) The structure shown is a protonated aldehyde, we will discuss the
chemistry of these next semester. All non-bonding electrons and formal charges are shown.
a) What is the hybridization of the oxygen atom?
the oxygen is sp2 hybridized
O
H3C
C
H
H
b) This next question asks if you know what hybridization really means. Give a list of ALL of the
atomic orbitals that the oxygen uses in this molecule according ot the hybridization model, AND,
state exactly how the oxygen uses each one, e.g. the oxygen uses an sp3 orbital to make a π-bond
to sulfur, it uses a p orbital to hold a non-bonding pair of electrons, it uses an sp orbital to make a
σ-bond to nitrogen, etc. (I know that these examples are nonsense, they are just to illustrate
the FORMAT you should use to answer the question)
the oxygen uses an sp2 hybridized atomic orbital to make a sigma-bond to carbon
the oxygen uses an sp2 hybridized atomic orbital to make a sigma-bond to hydrogen
the oxygen uses an sp2 hybridized atomic orbital to hold the non-bonding pair of electrons
the oxygen uses a p atomic orbital to make a pi-bond to carbon
c) Directly ON TOP of the protonated aldehydes that are redrawn for you below, draw a picture of
the Ψ OR Ψ2 as requested, for the indicated orbitals, AND, in each case write down the atomic
orbital or orbitals that you used, as appropriate
H
H
O
sp3 A.O. on carbon
H3C
O
C sp2 A.O. on carbon
H
Ψ for the C-C σ M.O. (ignore any
influence of hybridization on
electronegativity)
sp2 A.O. on carbon
C
H3C
H
1s A.O. on
hydrogen
Ψ2 for the C-H σ* M.O.
Question 6 (16 pts). Give line-angle structures for both stereoisomers of the following
condensed formula. Do not forget to add all non-bonding electrons. Label each stereosiomer as
either cis- or trans-.
CH3CH2CHCHOCH3
O
O
cis-
trans-
-5-
CHEMISTRY 233, Fall 2016, MIDTERM #1
NAME
Question 7 (31 pts.)
a) Rank the bonds indicated A, B and C in terms of increasing bond dissociation energy, give a
brief explanation.
H
B
B < C
A
N H
<
H
smallest
largest
BDE
BDE
O
P
C
A
H
H
bond C is from H to the most electronegative and smallest element, C thus has the largest BDE
bond A is to the largest and least electronegative element, it thus has the smallest BDE
b) Draw an energy versus bond separation distance (rZ-H) diagram for homolysis of the three
bonds A, B and C above, all on the same diagram provided below. Clearly indicate which
diagram refers to which bond cleavage and clearly indicate the three bond dissociation energies.
Energy
BDE B
BDE C
BDE A
rZ–H
c) Treat homolytic bond dissociation as a simple chemical reaction. For BOND A below, add
the curved arrows to the structure that illustrate bond-breaking and show the products of
homolytic bond breaking (i.e. what you get after breaking the bond) on the "product side" of the
reaction arrow below.
A
H
H
H
H H
H H
C H
C H
C
C
H
H
C
C
C
C
+ H
H H
H H
H H
H H