Organic Chemistry Laboratory 2
Factors Affecting the Relative Rates of Electrophilic Aromatic
Justiniano, Priscilla Raiza N.
School of Chemical Engineering and Chemistry, Mapua Institute of Technology, Intramuros, Manila, Philippines
Experiment No.1, Submitted on August 6, 2011 at N402.
EXPERIMENT NUMBER ONE IS ALL ABOUT THE ELECTROPHILIC SUBSTITUTION OF AROMATIC COMPOUNDS. AROMATIC COMPOUNDS ARE THOSE ORGANIC COMPOUNDS WHICH HAVE BENZENE RING (CYCLOHEXA-1,3,5-TRIENE). AROMATIC COMPOUNDS ARE ALWAYS FOLLOWS THE SUBSTITUTION REACTION BECAUSE OF THE STABILITY OF THE BENZENE RING. IT WILL NOT PROCESS THE ELIMINATION, ADDITION OR REARRANGEMENT REACTION. THIS EXPERIMENT WILL DETERMINE THE FACTORS OF ELECTROPHILIC SUBSTITUTION ON DIFFERENT AROMATIC RINGS THUS IT WILL HAVE DIFFERENT REACTION RATES BECAUSE OF DIFFERENT STRUCTURE OF THE COMPOUNDS. DIFFERENT REACTION WILL YIELDS TO A CONCLUSION OF WHAT IS/ARE THE FACTOR/S OF ELECTROPHILIC SUBSTITUTION ON AN ORGANIC COMPOUND – AROMATIC COMPOUNDS.
There are three experiments in this chapter of the laboratory. First is the substitution by bromination. Second is the solvent effect which is dealing in the nature of the solvent. And third is the temperature test. Having this division in the experiment one, we can now conclude that substituent in substitution, the nature of the solvent polar or non-polar and the temperatures are the factors of electrophilic substitution on aromatic compounds.
The most common reaction of aromatic compounds is electrophilic substitution. It is when an electron-poor reagent (an electrophile, E+) reacts with the electron-rich aromatic ring ( a nucleophile) and substitutes for one of the ring hydrogen. Electrophilic Substitution has several factors that affect its relative rates and this includes the following: substituents, solvent and temperature. Substituent like –OH and Br has an effect in electrophilic aromatic substitutions. All activating groups are ortho- and para- directing, and all deactivating groups other than halogen are meta directing. The halogens are ortho- and para- directing deactivators. The activation or deactivation of the benzene ring toward electrophilic attack, and electron withdrawing substituents deactivate the ring. Using the reagents benzene, chlorobenzene, aspirin, acetanilide, p-nitrophenol, anisole and phenol in ethyl acetate, we will observe the bromination rate and will classify as either activator or deactivator. In performing the experiment, 0.20 ml of bromine solution will be added in each solution.
In general terms, the choice of solvent can have a significant effect on the performance of a reaction. For an SN1 reaction, the polarity and ability of the solvent to stabilize the intermediate carbocation is of paramount importance. For an SN2 reaction, the effect of solvent polarity is usually much less, but the ability (or really lack thereof) of the solvent to solvate the nucleophile is the important. Using the two solvents cyclohexane, non-polar, and acetic acid, polar, we will determine the reaction rate of bromination in anisole.
Another thing that must be considered is the temperature. Typically heat will speed up a chemical reaction because it causes the actual atoms to move quicker and collide with each other causing a chemical reaction. In this experiment we are given three different temperature and we will going to determine the trend occurred as we increase the temperature during the bromination of acetanilide.
The Reagents used are the following:
0.2 M solutions in ethyl acetate of the following:
a. Benzene - is an organic chemical compound with the molecular formula C6H6. It is sometimes abbreviated Ph–H. Benzene is a colorless and highly flammable liquid with a sweet smell and a relatively high melting point....