Part C-Does the information written below this Table sound correct? It is part o
ID: 1018723 • Letter: P
Question
Part C-Does the information written below this Table sound correct? It is part of a larger report but I'm just concerned with the last part here.
Table 1 – Results
Compound
Time for Color Disappearance
>20 minutes
Ran at 0 °C
Diphenylamine
Instantaneous
(also formed a precipitate)
N/A
Instantaneous
(also formed a precipitate)
Phenol
Instantly lost color and turned yellow. After 30 seconds, turned clear.
N/A
Instantly turned yellow. After 52 seconds, turned clear.
N-Methylanaline
Instant color disappearance
N/A
Color disappearance after 60 seconds
Diphenylether
After 30 seconds, lost color and turned yellow
N/A
N/A
Anisole
Instant change to pale orange and after 150 seconds, turned yellow
N/A
N/A
Acetanilide
Turned pale orange at 90 seconds
Remained pale orange (some reactivity but not complete)
N/A
4-Bromophenol
Was pale orange at 180 seconds and at 5 minutes
Remained pale orange (some reactivity but not complete)
N/A
4-Hydroxybenzoic acid
Faded to orange at 180 seconds and stayed orange after 5 minutes
Turned a pale orange at 20 minutes
N/A
Bromobenzene
Red-orange at 5 minutes
Remained orange-red at 20 minutes
N/A
Benzoic Acid
Red-orange at 5 minutes
Remained orange-red at 20 minutes
N/A
Nitrobenzene
No reaction after 5 minutes
No reaction after 20 minutes
N/A
The final set of aromatic compounds consisted of bromobenzene, benzoic acid and nitrobenzene. All three compounds contained deactivating substituents with bromobenzene containing the least deactivating substituent and nitrobenzene containing the most deactivating substituent. In addition, bromobenzene is ortho/para directing while benzoic acid and nitrobenzene contain meta directing substituents. Both the bromobenzene and the benzoic acid turned a red-orange color at 5-minutes and remained that red-orange color even after 20 minutes. This was indicative that some reaction was occurring but at an extremely, slow rate. The nitrobenzene showed no reaction after 5 minutes and no reaction after 20 minutes, as expected, due to it being a very strong deactivator. It was thought that the bromobenzene would not have reacted at the same rate as the benzoic acid due to the –Br substituent being a weaker deactivator than the carbonyl substituent on the benzoic acid. This may have been noted had the reactions been done at 0 °C, although the process would have been even slower than what it already was.
Table 1 – Results
Compound
Time for Color Disappearance
>20 minutes
Ran at 0 °C
Diphenylamine
Instantaneous
(also formed a precipitate)
N/A
Instantaneous
(also formed a precipitate)
Phenol
Instantly lost color and turned yellow. After 30 seconds, turned clear.
N/A
Instantly turned yellow. After 52 seconds, turned clear.
N-Methylanaline
Instant color disappearance
N/A
Color disappearance after 60 seconds
Diphenylether
After 30 seconds, lost color and turned yellow
N/A
N/A
Anisole
Instant change to pale orange and after 150 seconds, turned yellow
N/A
N/A
Acetanilide
Turned pale orange at 90 seconds
Remained pale orange (some reactivity but not complete)
N/A
4-Bromophenol
Was pale orange at 180 seconds and at 5 minutes
Remained pale orange (some reactivity but not complete)
N/A
4-Hydroxybenzoic acid
Faded to orange at 180 seconds and stayed orange after 5 minutes
Turned a pale orange at 20 minutes
N/A
Bromobenzene
Red-orange at 5 minutes
Remained orange-red at 20 minutes
N/A
Benzoic Acid
Red-orange at 5 minutes
Remained orange-red at 20 minutes
N/A
Nitrobenzene
No reaction after 5 minutes
No reaction after 20 minutes
N/A
Explanation / Answer
Bromobenzene: is an aryl halide, C6H5Br, which can be formed by electrophilic aromatic substitution of benzene using bromine.
It is a clear, colourless or pale yellow liquid. It is soluble in methanol and diethyl ether, and very slightly soluble in cold water.
Lower bromobenzenes are clear liquid at room temperature while higher bromobenzenes are white to yellowish solids. They are practically insoluble in water and denser than water. . The water solubility is decreasing if more brominated.
Benzoic Acid: Benzoic acid is a solid, white crystalline substance that is chemically classified as an aromatic carboxylic acid. Its molecular formula may be written as C7H6O2. Its chemical properties are based on the fact that each molecule consists of an acidic carboxyl group attached to an aromatic ring structure. The carboxyl group can undergo reactions to form products such as salts, esters, and acid halides. The aromatic ring can undergo reactions such as sulfonation, nitration and halogenation.
Nitrobenzene: is an organic compound with the chemical formula C6H5NO2. It is a water-insoluble pale yellow oil with an almond-like odor. It freezes to give greenish-yellow crystals.
When substituted benzene molecules undergo electrophilic substitution reactions, substituents on a benzene ring can influence the reactivity. Activating substituents that activate the benzene ring toward electrophilic attack can alter the reaction rate or products by electronically or sterically affecting the interaction of the two reactants. deactivating substituents removes electron density from the benzene ring, making electrophilic aromatic substitution reactions slower and more difficult than benzene itself. For example, a hydroxy or methoxy substituent in phenol and anisole increases the rate of electrophilic substitution, while a nitro substituent decreases the ring's reactivity. Electron donating substituents activate the benzene ring toward electrophilic attack, and electron withdrawing substituents deactivate the ring, making it less reactive to electrophilic attack. The strongest activating substituents are the amino (-NH2) and hydroxyl (-OH) groups.
Reactivity Effects
Activating substituents
Deactivating substituents
Strong
-NH2, -NHR, -NR2, -OH, -O-
-NO2, -NR3+, -CF3, CCl3
Moderate
-NHCOCH3, -NHCOR, -OCH3,-OR
-CN, -SO3H, -COOH, -COOR, -COH, -COR
Weak
-CH3, -C2H5, -R, -C6H5
-F, -Cl, -Br, -I
Toluene, aniline and phenol are activated aromatic compounds. Examples of deactivated aromatic compounds are nitrobenzene, benzaldehyde and halogenated benzenes.
Activating substituents generally direct substitution to the ortho and para positions where substitutions must take place. With some exceptions, deactivating substituents direct to the meta position. Deactivating substituents which orient ortho and para- positions are the halogens (-F, -Cl, -Br, -I) and -CH2Cl, and -CH=CHNO2
When disubstituted benzene molecules undergo electrophilic substitution reactions, a new substituent is directed depends on the orientation of the existing substituents and their individual effects; whether the groups have cooperative or antagonistic directing effects. Ortho position is the most reactive towards electrophile due to the highest electron density ortho positions. But this increased reactivity is countervailed by steric hindrance between substituent and electrophile.
Reactivity Effects
Activating substituents
Deactivating substituents
Strong
-NH2, -NHR, -NR2, -OH, -O-
-NO2, -NR3+, -CF3, CCl3
Moderate
-NHCOCH3, -NHCOR, -OCH3,-OR
-CN, -SO3H, -COOH, -COOR, -COH, -COR
Weak
-CH3, -C2H5, -R, -C6H5
-F, -Cl, -Br, -I
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