ORGANIC CHEMISTRY DIAGNOSTIC TEST
Prepared by David Jeffrey, Ph.D.,
Cost Benefit, LLC, www.costbenllc.com
Online tutorials, virtual classroom, educational consultations, course development, course support materials, diagnostic tests, program and career advising
Multiple choice. Circle the letter, a, b, c, or d, corresponding to the best answer:
Lewis structures do not account for/provide:
octets
formal charges
resonance
molecular shape
When more than one valid Lewis structure may be drawn for the same molecular formula, these multiple structures:
must be isomers
must be resonance forms
must be either isomers or resonance forms
must be octet rule exceptions
Exceeding the octet rule:
is possible for atoms that two lone electron pairs
is possible for atoms that have three valance electrons
is not possible
is possible for third row and higher atoms
The ‘octet rule’ is based on the special stability of:
Group II elements
Group IV elements
Group VI elements
Group VIII elements
Multiple resonance forms:
all refer to one molecule
must all have the same ‘% contributions’
refer to multiple molecules
do not have to all be valid Lewis structures
‘Skeletal structures’ have implied:
formal charges
double bonds
hydrogens
oxygens
Carbon tetrachloride has the molecular formula, CCl4. It has a ______________ shape, from ____________ theory.
trigonal planar, VSEPR
square planar, Lewis structure
tetrahedral, VSEPR
octahedral, VSEPR
Atoms hybridize their orbitals in order to:
increase their acidity or improve orbital overlap
improve overlap or achieve an octet
achieve an octet or have resonance
have resonance or increase acidity
All alkanes:
have the molecular formula, CnH2n+2
have the formula, CnH2n
have no double or triple bonds
none of the above
A Bronsted-Lowry acid must:
have a CO2H group somewhere in the molecule
have an OH group......
must have a H.......
must have a lone pair
The stronger the acid, the….
greater the pKa
smaller the pKa
higher the pH
smaller the Kab
Alkanes undergo very few reactions. The reason for this is:
their molecular weights are too small
they don’t have enough carbon atoms
they don’t have enough hydrogen atoms
they lack functional groups
Alkanes under combustion reactions with ____, to produce ___, ____, and ____.
water, oxygen, CO2, energy.
oxygen, chlorine radicals, water, carbon dioxide.
oxygen, CO2, water, energy.
bromine, radicals, oxygen, water.
The three stages of a radical chain reaction are, in order:
initiation, condensation, and termination
deprotonation, propagation, and condensation
initiation, propogation, and termination
propogation, initiation, and termination
For any given acid-base reaction, in order for the Kab to lie to the right:
the pKa of the acid must be greater than the pKa of the conjugate acid
the pKa of the acid must be less than the pKa of the conjugate acid
the pKa of the conjugate acid must be less than the pKa of the acid
the pH of the conjugate acid must be greater than the pH of the acid
The combustion of an alkane is what type of general reaction?
radical reaction
acid-base reaction
oxidation-reduction reaction
none of the above
“Conformers”:
are another type of “isomer”
involve torsional angle rotation
involve bond angle rotation
are non-superimposable mirror images
Two substituents on a cyclohexane ring have a ‘cis-1,3’ relationship. This means they can be:
axial, axial
axial, equatorial
equatorial, axial
boat, chair
We generally show relative stereochemistry using cyclic compounds because:
acyclic compounds only have absolute stereochemistry
cyclic compounds are generally more stable than acyclic
cyclic compounds have fewer conformational states
cyclic compounds have no bond angle strain
Enantiomers:
must be superimposable mirror images
must have the same number of chiral carbons, but may have different achiral carbons
cannot be separated
have the same sign but different magnitudes of []
For a structure with “n” chiral carbons, but fewer than “2n” distinct stereoisomers, there must be:
an axis of symmetry in the molecule
an odd number of “n”
an even number of “n”
a ring in the structure
Circle the molecule expected to prefer Sn2 over Sn1:
Circle the alkyl halide expected to prefer Sn1 over Sn2:
Circle the alkyl halide which may react via Sn1 or Sn2:
Based on our lectures, which of the following methods does not tell us whether a secondary alkyl halide prefers Sn1 or Sn2?
stereochemical test
rate study
detection of reactive intermediates
changing the leaving group
Any chemical reaction which results in the creation of one new chiral carbon, from an achiral reactant. and which lacks any special chiral catalyst or reagent:
generally prefers the R-enantiomeric product
must always give a racemic mixture of products
generally prefers the S-enantiomeric product
must always give a diastereomeric mixture of products
“Syn” and “anti” refer to:
regiochemistry of the E2 reaction
double-bond substitution
stereochemistry of the E2 reaction
none of the above
For a general alkene addition reaction, we are concerned with the regiochemistry only for:
nonsymmetric alkene + symmetric “X-Y”
nonsymmetric alkene + nonsymmetric “X-Y”
symmetric alkene + symmetric “X-Y”
symmetric alkene + nonsymmetric “X-Y”
Consider the following reaction of some alkene:
C6H10 + CH3CH2OH --------- (cat H+) -------> C8H16O
What can you say about the structure of the product?
must be a cyclic alcohol
must be a cyclic ether
must be an acyclic alcohol
must be an acyclic ether
Hydroboration of an nonsymmetric alkene results in:
a Markovnikov alcohol as the major product
a cis epoxide
a trans epoxide
an anti-Markovnikov alcohol as the major product
The reaction of cis-2-butene with HBr gives:
a cis epoxide
mainly (2R)-2-bromobutane
mainly (2S)-2-bromobutane
racemic 2-bromobutane
An “E1” reaction always involves a total of ____ steps:
Two
Three
Four
depends on the reactant
An alcohol may be _________ to convert it into a better leaving group:
“hydroborated”
“tosylated”
Reduced
oxidized
You react an acyclic molecule with H2SO4 and obtain a cyclic ether as the product. Your reactant must have been:
an ‘alcohol alkene’
an ‘alcohol ether’
an ‘alkene bromide’
an ‘epoxide alkene’
Draw a valid Lewis structure for each molecular formula. Show the ‘full Lewis structure’, no shorthand conventions:
35) [C3H5O]-
36) HN3
37) C2Cl4
38) [O2]2-
Convert each of the following Lewis structures to skeletal, or skeletal to Lewis, as indicated:
Predict the following reactions by drawing the expected product(s) in the boxes provided. Ignore any stereochemical aspects. Your product(s) should be consistent with any additional reaction information which may be presented:
Using the pKa table attached to the exam, or your basic qualitative knowledge of how structure affects acidity, draw the products of the following acid-base reactions in the boxes provided. Then, estimate the position of the acid-base equilibrium reaction by selecting the appropriate Kab choice:
For each of the following two problems, circle one of the last four structures that has the indicated relationship to the first structure:
For each of the following nucleophilic substitution reactions, draw the expected product(s) in the boxes provided. Show absolute and/or relative stereochemistry as applicable. Additional information or data may be provided for assistance:
Explanation:
61) We never draw five or more bonds to carbon atoms in molecules. For an uncharged carbon, we always show four bonds: 4 single bonds, or 1 double and 2 singles, or 2 doubles, or 1 triple and 1 single…..
……WHY?!
Provide an explanation for this rule, based on the electron configuration of a carbon atom, Valence Bond Theory (VBT), and any other related topics we’ve discussed in lecture:
62) The following reaction converts the cyclic hydrocarbon (A) to benzene (B) and hydrogen gas. While this is known to be an oxidation reaction, show, by oxidation states, that this is indeed true:
63) The radical halogenation of the alkene, propene, proceeds much more rapidly than the same reaction for propane. Additionally, the halogen atom is incorporated at a primary position in propene, while propane prefers the expected secondary halogenation.
While we haven’t studied alkene chemistry, use what you know about the radical halogenation mechanism….and resonance….to propose an explanation for this observation. You may use a verbal explanation to support your proposed structures and mechanism, but this can’t be your sole explanation:
For each of the following reactions, draw the expected product(s) in the boxes provided. Show absolute and/or relative stereochemistry as applicable. Your answers must be consistent with any additional information or data:
Synthesis. Show the reactions you would use to go from the indicated starting material to the target molecule. You must show the expected product(s) from each of your proposed reaction steps:
FOR A FREE ANALYSIS OF YOUR TEST RESULTS, EMAIL ME AT: djeffrey@costbenllc.com