Lab 6: Electrophilic Aromatic Substitution

Two forms of stereochemistry can form product for the bromination of trans-cinnamic acid. Cis addition, also known as syn addition, is one way of forming product. This form of stereochemistry allows for the components of the reagent to add to the same side of the double bond. Trans, also known as anti addition, is the second form of addition that can create product for this experiment. Tran stereochemistry occurs when the components of the reagent add to opposite sides of the double bond. In this experiment, the formation of either erythro-2,3-dibromo-3-phenylpropanoic acid (trans/anti-R,S or S,R) or threo-2,3-dibromo-3-phenylpropanoic acid (cis/syn-R,R or S,S) was expected to occur.

Theory: One of the methods of preparing alkyl halides is via the nucleophilic substitution reactions of alcohols. Alcohols are inexpensive materials and easy to maintain. However, they are a poor leaving group the OH group is a problem in nucleophilic substitution, this problem is fixed by converting the alcohol into H2O.

As detailed in Pavia 's Organic Laboratory techniques the reaction is expected to proceed via the following reaction:

Mayo, D. W.; Pike, R. M.; Forbes, D. C. Microscale Organic Laboratory with Multistep and Multiscale Syntheses, 5th ed.; John Wiley & Sons, Inc., 2011; pp 132-135.

Because there are steric hindrance of two methyl groups on 4th carbon, the hydride is added to the endo side of the carbonyl group. 3. Reduction of Camphor produces a mixture of diastereomers. 4.

The objective of this laboratory experiment is to study both SN1 and SN2 reactions. The first part of the lab focuses on synthesizing 1-bromobutane from 1-butanol by using an SN2 mechanism. The obtained product will then be analyzed using infrared spectroscopy and refractive index. The second part of the lab concentrates on how different factors influence the rate of SN1 reactions. The factors that will be examined are the leaving group, Br – versus Cl-; the structure of the alkyl group, 3◦ versus 2◦; and the polarity of the solvent, 40 percent 2-propanol versus 60 percent 2-propanol.

Gilbert, John and Stephen F. Martin. Experiment Organic Chemistry: A Miniscale & Microscale Approach. Belmont, CA: Thomson Brooks/Cole, 2010. 537-547. Print.

6. Purpose: to clarify the mechanism for the cycloaddition reaction between benzonitrile oxide and an alkene, and to test the regiochemistry of the reaction between benzonitrile oxide and styrene; to purify the crude product of either trans-stilbene, cis-stilbene, or styrene reaction.

The purpose of this experiment is to examine the reactivities of various alkyl halides under both SN2 and SN1 reaction conditions. The alkyl halides will be examined based on the substrate types and solvent the reaction takes place in.

Dictionary of organic compounds, 6th edition, Chapman and Hall, London, Volume 3(& Volume 6), 1996 Maria Lindsay and Sean P. Hickey, Organic chemistry lab 2 manual, department of Chemistry University of New Orleans

Fifield, F. W. and Kealey, D. 1995. Principles and Practice of Analytical chemistry. (4th ed) Glasgow, Blackie Academic and professional.

Aromatic compounds can undergo electrophilic substitution reactions. In these reactions, the aromatic ring acts as a nucleophile (an electron pair donor) and reacts with an electrophilic reagent (an electron pair acceptor) resulting in the replacement of a hydrogen on the aromatic ring with the electrophile. Due to the fact that the conjugated 6π-electron system of the aromatic ring is so stable, the carbocation intermediate loses a proton to sustain the aromatic ring rather than reacting with a nucleophile. Ring substituents strongly influence the rate and position of electrophilic attack. Electron-donating groups on the benzene ring speed up the substitution process by stabilizing the carbocation intermediate. Electron-withdrawing groups, however, slow down the aromatic substitution because formation of the carbocation intermediate is more difficult. The electron-withdrawing group withdraws electron density from a species that is already positively charged making it very electron deficient. Therefore, electron-donating groups are considered to be “activating” and electron-withdrawing groups are “deactivating”. Activating substituents direct incoming groups to either the “ortho” or “para” positions. Deactivating substituents, with the exception of the halogens, direct incoming groups to the “meta” position. The experiment described above was an example of a specific electrophilic aromatic

one acetyl group to an aromatic ring or add two acetyl groups to each of the

In this experiment, benzopinacol was to be synthesized through photochemical reaction and its acid-catalyzed rearrangement product benzopinacolone.

Aromatic compounds tend to undergo electrophilic aromatic substitutions rather than addition reactions. Substitution of a new group for a hydrogen atom takes place via a resonance-stabilized carbocation. As the benzene ring is quite electron-rich, it almost always behaves as a nucleophile in a reaction which means the substitution on benzene occurs by the addition of an electrophile. Substituted benzenes tend to react at predictable positions. Alkyl groups and other electron-donating substituents enhance substitution and direct it toward the ortho and para positions. Electron-withdrawing substituents slow the substitution and direct it toward the meta positions.