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



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


structure and bonding, pi-bonds


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)


addition of carbocations

radical additions

add groups to both ends simultaneously and stereospecifically

catalytic hydrogenation




add stereospecifically to "make a triangle"





post-pattern occurances:

trapping by nucleophiles or radicals



carbon-carbon bond cleavage


regio- and stereoselectivity issues

thermodynamic and kinetic control


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


structure and bonding, perpendicular pi-bonds

some physical properties

NMR and IR spectroscopy

preparation via elimination

acidity and alkynyl anions

analogies with alkene reactions


addition of electrophiles

regiochemical issues

vinyl halides


Delocalized pi-Systems (V&S Chapter 14)

conjugation gives color

conjugation: resonance and MOs



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



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


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


"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




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):




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


amino groups and amides (N-linked)

alcohols, ethers and esters (O-linked)

hyperconjugating alkyl groups

deactivating and meta-directing (by default)


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


competing substituents

potential problems

substituents that react with electrophiles

synthetic strategies, the order of reactions is key!

extending the pattern to polycycles




The Carbonyl Group (V&S Chapter 17)

pi-systems containing oxygen, everyone knows acetone

analytical tools: Fehling's and Tollens' tests


structure and bonding; heteroatoms and lone pairs


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



acetalization and ketalization


imine formation

cyanohydrin formation

addition of phosphorous ylides

addition of peracids

relative reactivities/electrophilicities


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!)





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