Orgo Lab 2 - Lab report for Electrophilic Aromatic Substitution PDF

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Lab report for Electrophilic Aromatic Substitution...

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Madison Fisher Malorie Hacker February 13, 2019

Electrophilic Aromatic Substitution Objective: The objective of this lab is to classify the relative bromination rates of activated and deactivated substituted benzenes compared with ethyl benzene, to correlate the rate of bromination with the electronic properties of the aryl substituents, to brominate acetanilide and isolate the product via liquid/liquid extraction, and to determine the substitution pattern (ortho, meta or para) of the product by a comparative TLC.

Experimental: To begin this lab, a warm water bath was prepared in a 250 mL beaker. The beaker was filled ⅔ of deionized water and a 50 mL beaker was placed inverted inside to ensure the test tubes did not fall. While the hot water bath heated on the hot plate to 370 C, seven test tubes were prepared. In the test tubes, 1 mL of the following was place in its own tube: ethyl benzene, chlorobenzene, anisole, phenol, benzaldehyde, nitrobenzene, and acetanilide. The tubes were placed in the water bath. After the tubes were allowed to heat for 5 minutes, bromine solution (0.05 M, 1.5mL) was added to each, swirled, corked, and placed back into the water bath. The solution was timed from the addition of the bromine to the disappearance of the yellow color loss. The reaction time for each compound was identified as very rapid, fast, slow, very slow or no reaction relative to ethyl benzene. Once acetanilide was in the water bath for one hour, an isolation of brominated acetanilide was done by extraction. To begin part two of the lab, the mixture of brominated acetanilide was transferred into a plastic conical test tube and diluted with deionized water (1mL). NaOH (1mL. 10M) was added added to the solution and pH tested until the solution was basic. This was repeated 4 times. Ethyl Acetate (2mL) was added to the mixture, shaken, and allowed to settle. The product was on the top as the organic layer. To identify the substitution pattern a comparative TLC was taken.

Madison Fisher Malorie Hacker February 13, 2019

Results and Discussion: Data: Electrophilic Aromatic Substitution Compound

Structure

ortho-para director or meta director

Activating or Deactivating

Reaction Time (minutes)*

Reaction Rate**

ethyl benzene

ortho-para director

Activating

1hr

chlorobenzene

ortho-para director

Deactivating

1hr, still very yellow

VS or NR

anisole

ortho-para director

Activating

32 minutes

F

phenol

ortho-para director

Activating

53 seconds

VR

benzaldehyde

meta director

Deactivating

1 hr, still very yellow

VS or NR

nitrobenzene

meta director

Deactivating

1 hrs, till very VS or NR yellow

acetanilide

ortho-para director

Activating

46 minutes

S

Madison Fisher Malorie Hacker February 13, 2019

Rf Values Product A

0.55

o-bromoacetanilide

0.73

m-bromoacetanilide

0.64

p-bromoacetanilide

0.55

5.3

O A M P Calculations: Rf value of o-bromoacetanilide: Rf value = 4.0cm / 5.30cm

Madison Fisher Malorie Hacker February 13, 2019

= 0.73 Rf value of Product (A): Rf value = 3.0cm / 5.30cm = 0.55 Rf value of m-bromoacetanilide: Rf value = 3.5cm / 5.30cm = 0.64 Rf value of p-bromoacetanilide: Rf value = 3.0cm / 5.30cm = 0.55 Discussion: Once the bromine was added to the ethyl benzene, chlorobenzene, anisole, phenol, benzaldehyde, nitrobenzene, and acetanilide test tubes the mixture turned yellow. In relative to ethyl benzene, chlorobenzene, benzaldehyde, and nitrobenzene were all very slow or non reactive. The mixtures also did not change color. These are considered deactivating. Anisole became colorless in 32 minutes-fast, phenol in 58 seconds- very fast,- and acetanilide in 46 minutes- slow. Each of these are considered activating. In part two, a successful isolation of brominated acetanilide was performed by extraction. A comparative TLC concluded that pbromoacetanilide was the product. The Rf values were 0.55 for the product (A), 0.73 for obromoacetanilide, 0.64 for m-bromoacetanilide, and 0.55 for p-bromoacetanilide. This concluded that the product’s substituent pattern was p-bromoacetanilide.

Conclusion: Bromination rates were classified as activated and deactivated substituted benzenes compared with ethyl benzene. Acetanilide was brominated and the product was isolated via liquid/liquid extraction. P-bromoacetanilide was determined to be the substitution pattern via a TLC...