Syllabus
This course will examine the physical properties, reactions and applications of organic molecules containing pi-systems.
Texts and Tools:
Vollhardt, K. P. C. and Schore, N. E. Organic Chemistry: Structure and Function, 4th Edition. Freeman, 2003.
Molecular models.
Friedrich, E. C.; Takahashi, J.; Spence, J. D. Chem 118B Supplementary Laboratory Book.
Pavia D. L.; Lampman, G. M.; Kriz, G. S.; Engel, R. G. Introduction to Organic Laboratory Techniques, 3rd Edition. Saunders, 1998.
My Expectations:
A working knowledge of the material covered in Chem 118A is essential.
This class is not about memorization. It is about developing analytical thinking and problem-solving skills .
The specific skills we will develop are:
proposing reasonable arrow-pushing mechanisms for reactions that involve organic pi-systems
identifying the structures of organic molecules with pi-systems by integrating spectroscopic and other experimental observations
explaining the origins of regio- and stereoselectivity for reactions that involve organic pi-systems
predicting the reactivity of organic pi-systems with particular reagents
applying the reactions of organic pi-systems to the planning of multistep syntheses
Policies
laboratory: All laboratory assignments must be completed in order to receive a passing grade for this course.
make-up exams: No early or late exams (midterms or final) will be given. For students with a legitimate reason for missing a midterm (written documentation of the reason for such an absence is required), the final examination (since it is cumulative) will be scaled to count for 350 points.
final exam: You must take the final exam in order to pass this class. Students who miss the final examination will receive a grade of "incomplete" only if written documentation of a legitimate reason for their absence is provided and they have a passing grade going into the final exam.
regrades: Aside from errors in totaling points, regrading will only be performed for requests of 5 or more points. If you think you deserve at least 5 more points than you were given on an exam, you may request a regrade. To do so, you must describe, in writing, why you think you deserve additional points and submit this request, along with your exam, to your TA within one week of the day your exam was returned. Do not make any changes to or marks on your exam or you will forfeit the right to a regrade. Keep in mind that the entire exam will be regraded. Your TA will return the exam to you after it is regraded.
mutual respect: We are all adults and should treat each other as such. Cheating of any kind (including plagiarism, beginning an exam early, continuing to write on an exam after time is called) will not be tolerated.
Strategies for Success
work lots of problems: You cannot work too many problems. The problems in the textbook and the "problems-of-the-day" are representative of the types of problems you will encounter on the midterms and the final exam. Remember, you will not have the study guide with you during exams, so you must practice until you can solve problems without it. Be sure to practice all types of problems (synthetic, mechanistic, spectroscopic, explain, and problems that combine them).
build models: Build models whenever you can. This is especially important for solving problems that deal with regio- and stereoselectivity.
patterns: Believe it or not, Organic Chemistry is not about memorization. It is actually about pattern recognition. Everything fits into a pattern (or is extremely interesting because it does not). Your goal should be to discover the patterns (I will help!) and practice recognizing them. If you can learn this skill, you will be able to answer almost any problem thrown at you, whether or not you've previously memorized the details of the particular case in question. Here's a little secret: exam-writers often try to make problems seem difficult by adding "spinach" to molecules that might distract you from seeing the relevant pattern(s) (while this is tricky, it is also representative of most organic chemistry problems encountered in real research!). So, another goal should be to become comfortable with cutting through the spinach so you can focus on the pattern; i.e. find the part of a molecule (functionality) that you have learned about or that is analogous to something you have learned about.
don't wait: Reread your notes and work problems after every lecture. Last minute cramming rarely works in an Organic Chemistry class.
additional resources: Many great tips can be found at Saundra McGuire's website (of particular relevance is her "Acing Organic Chemistry" presentation). UCD also has a Learning Skills Center, which, among other things, holds regular workshops.
just me?: I view chemistry problems as puzzles or games and have always liked building models because they are like toys. This does not mean that anything in this class should be taken lightly. It does mean that you should try to find some way to make problem solving fun.
Outline (subject to change):
Alkenes and Infrared Spectroscopy (V&S Chapter 11)
alkenes in nature, pheromones
nomenclature
structure and bonding, pi-bonds
acidity
stability trends
NMR spectroscopy
intro to IR spectroscopy
degree of unsaturation
preparation via elimination
Reactions of Alkenes (V&S Chapter 12)
intro to addition reactions
the three reactivity patterns:
add a group to one end (possible scrambling of stereochemistry)
protonation
addition of carbocations
radical additions
add groups to both ends simultaneously and stereospecifically
catalytic hydrogenation
hydroboration
dihydroxylation
ozonolysis
add stereospecifically to "make a triangle"
halogenation
epoxidation
cyclopropanation
oxymercuration
post-pattern occurances:
trapping by nucleophiles or radicals
oxidation
reduction
carbon-carbon bond cleavage
polymerization
regio- and stereoselectivity issues
thermodynamic and kinetic control
sterics
cation and radical stabilities, (hyper)conjugation
anti additions are stepwise
syn additions are usually concerted
Markovnikov terminology
Alkynes (V&S Chapter 13)
alkynes in nature, poisons and cures
nomenclature
structure and bonding, perpendicular pi-bonds
some physical properties
NMR and IR spectroscopy
preparation via elimination
acidity and alkynyl anions
analogies with alkene reactions
reductions
addition of electrophiles
regiochemical issues
vinyl halides
Delocalized pi-Systems (V&S Chapter 14)
conjugation gives color
conjugation: resonance and MOs
allyl
butadiene
longer polyenes
cyclic polyenes (more in V&S Ch. 15)
UV-vis spectroscopy and color
acidity of allylic and propargylic positions
diene hydrogenation, stability
the four reactivity patterns:
taking advantage of allylic stabilization
allylic radicals
halogenation
polymerization
allylic cations
SN1 and SN2 reactions
natural product and rubber biosynthesis
allylic anions
organometallic nucleophiles
addition of electrophiles to dienes
comparison with alkenes
kinetic and thermodynamic control
cycloadditions
Diels-Alder in detail
concerted, stereospecific
endo vs. exo selectivity
electrocyclic reactions
heat vs. light
orbital arguments
similarities and differences with cycloadditions
Benzene and Aromaticity (V&S Chapter 15)
possible isomers
nomenclature
"unusual" or "extra" stability
structure and bonding, cyclic conjugation
"aromaticity", Huckel's 4n+2 Rule and planarity
UV-vis, NMR and IR spectroscopy
other aromatic systems
polycyclic aromatic hydrocarbons
carbon allotropes
perimeters and substructures
annulenes
ions
heterocycles
aromatic transition structures
avoiding antiaromaticity; settling on nonaromatic
bond localization
becoming nonplanar
facile reduction/oxidation
Electrophilic Aromatic Substitution (V&S Chapters 15&16)
drugs containing benzene units; synthetic strategies
PAHs and cancer
the general reaction and its mechanism (V&S Ch. 15-8)
substitution vs. addition; regaining aromaticity
applying the pattern (V&S Ch. 15-9 through 15-13):
halogenation
nitration
sulfonation
Friedel-Crafts alkylation
Friedel-Crafts acylation
regiochemistry; three patterns on top of the basic pattern (V&S Ch. 16):
mechanistic reasoning; reactants, TSs, intermediates
activating and ortho/para-directing
pi-donors
amino groups and amides (N-linked)
alcohols, ethers and esters (O-linked)
hyperconjugating alkyl groups
deactivating and meta-directing (by default)
pi-acceptors
aldehydes and ketones
acids, esters and amides (C-linked)
trifluoromethyl (sigma-withdrawing and non-pi)
deactivating and ortho/para-directing
pi-donating but very sigma-withdrawing
halogens
competing substituents
potential problems
substituents that react with electrophiles
synthetic strategies, the order of reactions is key!
extending the pattern to polycycles
naphthalene
phenanthrene
The Carbonyl Group (V&S Chapter 17)
pi-systems containing oxygen, everyone knows acetone
analytical tools: Fehling's and Tollens' tests
nomenclature
structure and bonding; heteroatoms and lone pairs
polarity
NMR and IR spectroscopy
preparation via reactions you've already seen:
oxidation of alcohols
ozonolysis of alkenes
hydration of alkynes
Friedel-Crafts acylation
the first reactivity pattern: nucleophiles adding to the carbonyl carbon
activation by protic or Lewis acids
hydrides
hydration
acetalization and ketalization
thioketalization
imine formation
cyanohydrin formation
addition of phosphorous ylides
addition of peracids
relative reactivities/electrophilicities
sterics
inductive effects
post-pattern occurances:
enamine formation (more in V&S Ch. 18)
Wolff-Kishner reduction/deoxygenation
Raney Ni reduction/deoxygenation
Wittig reaction
Baeyer-Villiger oxidation
The Carbonyl alpha-Position (V&S Chapter 18)
acidity of alpha-protons; enolates
the second reactivity pattern: alpha-deprotonation then nucleophilic attack
keto-enol equilibria (a rare attack on the oxygen!)
silyl enol ethers (another rare attack on the oxygen!)
deuteration
halogenation
alkylation
enamines
the aldol reaction
post-pattern occurances:
dehydration to form enones
properties of enones
preparation by isomerization into conjugation
previous patterns: reacting as carbonyls and alkenes
conjugate/Michael addition - patterns one and two combined
Robinson annulation
