(A) With HBr, anisole forms bromobenzene and methyl alcohol.
(R ) `Br^(-)` ion will combine with smaller group to avoid steric hindrance.
(A) With HBr, anisole forms bromobenzene and methyl alcohol.
(R ) `Br^(-)` ion will combine with smaller group to avoid steric hindrance.
(R ) `Br^(-)` ion will combine with smaller group to avoid steric hindrance.
A
If both assertion and reason are correct and reason is correct explanation for assertion.
B
If both assertion and reason are correct but reason is not correct for assertion.
C
If assertion is correct but reason is incorrect.
D
If both assertion and reason are incorrect.
Text Solution
AI Generated Solution
The correct Answer is:
To solve the problem, we need to analyze the reaction of anisole (methyl phenyl ether) with HBr and understand the mechanism involved.
### Step-by-Step Solution:
1. **Identify Anisole Structure**:
Anisole is represented as a benzene ring with a methoxy group (-OCH3) attached. Its structure can be depicted as:
\[
\text{C}_6\text{H}_5\text{-O-CH}_3
\]
2. **Reaction with HBr**:
When anisole reacts with HBr, the ether bond (C-O) is protonated. The oxygen atom in the methoxy group has a lone pair of electrons that can attract the hydrogen ion (H+) from HBr, leading to the formation of an oxonium ion:
\[
\text{C}_6\text{H}_5\text{-O-CH}_3 + \text{HBr} \rightarrow \text{C}_6\text{H}_5\text{-O}^+\text{-CH}_3 + \text{Br}^-
\]
3. **Formation of Oxonium Ion**:
The oxonium ion structure is:
\[
\text{C}_6\text{H}_5\text{-O}^+\text{-CH}_3
\]
Here, the oxygen carries a positive charge due to the protonation.
4. **Bond Strength Consideration**:
The bond between the oxygen and the methyl group (C-O) is weaker than the bond between the oxygen and the benzene ring (C-O). This is due to resonance stabilization in the latter bond, which gives it partial double bond character.
5. **Nucleophilic Attack**:
The bromide ion (Br^-) will perform a nucleophilic attack on the weaker bond (C-O) of the methyl group. This follows the SN2 mechanism, where the nucleophile attacks the less sterically hindered site:
\[
\text{C}_6\text{H}_5\text{-O}^+\text{-CH}_3 + \text{Br}^- \rightarrow \text{C}_6\text{H}_5\text{-OH} + \text{CH}_3\text{Br}
\]
6. **Products Formation**:
The products of this reaction are phenol (C6H5OH) and methyl bromide (CH3Br):
\[
\text{Products: Phenol and Methyl Bromide}
\]
7. **Conclusion**:
The assertion that anisole forms bromobenzene and methyl alcohol with HBr is incorrect. The correct products are phenol and methyl bromide. The reason provided is correct as the Br^- ion attacks the smaller alkyl group to avoid steric hindrance.
### Final Answer:
- Assertion: **Incorrect** (Anisole does not form bromobenzene and methyl alcohol).
- Reason: **Correct** (Br^- ion attacks the smaller group due to steric hindrance).
To solve the problem, we need to analyze the reaction of anisole (methyl phenyl ether) with HBr and understand the mechanism involved.
### Step-by-Step Solution:
1. **Identify Anisole Structure**:
Anisole is represented as a benzene ring with a methoxy group (-OCH3) attached. Its structure can be depicted as:
\[
\text{C}_6\text{H}_5\text{-O-CH}_3
...
Similar Questions
Explore conceptually related problems
Assertion (A): The Heat of ionisation of water is equal to the heat of neutralistion of a strong acid with a strong base. Reason (R ) : Water ionises to a very small extent while H^(o+) ions from from an acid combine very rapidly with overset(Theta)OH from a base to form H_(2)O .
Read the given passage and answer the questions number 1 to 5 that follow: The substitution reaction of alkyl halide mainly occurs by S_N 1 and S_N 2 mechanism. Whatever mechanism alkyl halides follow for the substitution reaction to occur, the polarity of the carbon halogen bond is responsible for these substitution reactions. The rate of S_N 1 reactions are governed by the stability of carbocation whereas for S_N 2 reactions steric factor is the deciding factor. If the starting material is a chiral compound, we may end up with an inverted product or racemic mixture depending upon the type of mechanism followed by alkyl halide. Cleavage of ethers with HI also governed by steric factor and stability of carbocation, which indicates that in organic chemistry, these two major factors help us in deciding the kind of product formed 1. Predict the stereochemistry of the product formed if an optically active alkyl halide undergoes substitution reaction by S_N 1 mechanism. 2. Name the instrument used for measuring the angle by which the plane polarised light is rotated. 3. Predict the major product formed when 2-Bromopentane reacts with alcoholic KOH. 4. Give one use of CHI_3 5. Write the structures of the products formed when anisole is treated with HI.
A hydrocarbon (A) (molecular formula ( C_(5)H_(10) ) yields 2-methyl butane on catalytic hydrogenation. (A) adds HBr (in accordance with Markonikov's rule) to form a compound (B), which on reaction with silver hydroxide forms an alcohol ( C ), C_(5)H_(12)O . Alcohol ( C ) on oxidation gives a ketone (D). Deduce the structure of (A), (B), ( C ) and (D) and show the reactions involved.
Establish the structure of a hydrocarbon C_5 H_(10) from the following facts : (i) The hydrocarbon yields 2-methyl butane on catalytic reduction. (ii) The hydrocarbon adds HBr to form a compound (B) which on reaction with moist silver oxide produces an alcohol (C). (iii) The alcohol (C) on oxidation gives a ketone containing the same number of carbon atoms.
Consider a solution of CH_3COONH_4 which is a salt weak acid and weak base. The equilibrium involved in the solutions are : CH_3COO^(-)+H_2OhArrCH_3COOH+OH^(-) " ........"(i) NH_(4)^(+)+H_(2)hArrNH_(4)OH+H^(+)" ........"(ii) H^(+)+OH^(-)hArrH_(2)O" ........"(iii) If we add these reactions, then the net reaction is : CH_(3)COO^(-)+H_(2)^(+)+H_(2)OhArrCH_(3)COOH+NH_(4)OH" ........"(iv) Both CH_(3)COO^(-) and NH_(4)^(+) get hydrolysed independently and their hydrolysis depends on : (a) their initial concentration (b) The value of K_(h) which is (K_(w))/(K_(a)) for CH_(3)COO^(-) and (K_(w))/(K_(b)) for NH_(4)^(+) . Since both of the ions were produced form the salt, their initial concertration are same. Therefore, unless and until the value of (K_(w))/(K_(a)) or K_(a) and K_(b) is same, the degree of hydrogen of ions can't be same. To explain why we assume that degree of hydrolysis of cation and anion is same, we needed to now look at the third reaction i.e.,combination of H^(+) and OH^(-) ions. It is obvious that this reaction happens only because one reaction produced H^(+) ion and the other prodcued OH^(-) ions. We can also note that this reaction causes both the hydrolysis reaction to occur more since their product ions are being consumed. Keep this in mind that the equilibrium which has smaller value of the equilibrium constant is affected more by the common ion effect. For the same reason if for any reson a reaction is made to occur to a greater extent by the consumption of any of the prodcut ion, the reaction with the smaller value of equilibrium constant tends to get affected more. Therefore, we conclude that firstly the hydroylsis of both the ions occurs more in the presence of each other (due to consumption of the product ions) than in each other's absence. Secondly,the hydroylsis of the ion which occurs to a lesser extent (due to smaller value of K_(h)) is affected more than the one whole K_(h) is greater. Hence we can see that the degree of hydroylsis of both the ions would be close to each other when they are getting hyderolysed in the presence of each other. In the hydrolysis of salt weak acid and weak base :
Consider a solution of CH_3COONH_4 which is a salt weak acid and weak base. The equilibrium involved in the solutions are : CH_3COO^(-)+H_2OhArrCH_3COOH+OH^(-) " ........"(i) NH_(4)^(+)+H_(2)hArrNH_(4)OH+H^(+)" ........"(ii) H^(+)+OH^(-)hArrH_(2)O" ........"(iii) If we add these reactions, then the net reaction is : CH_(3)COO^(-)+H_(2)^(+)+H_(2)OhArrCH_(3)COOH+NH_(4)OH" ........"(iv) Both CH_(3)COO^(-) and NH_(4)^(+) get hydrolysed independently and their hydrolysis depends on : (a) their initial concentration (b) The value of K_(h) which is (K_(w))/(K_(a)) for CH_(3)COO^(-) and (K_(w))/(K_(b)) for NH_(4)^(+) . Since both of the ions were produced form the salt, their initial concertration are same. Therefore, unless and until the value of (K_(w))/(K_(a)) or K_(a) and K_(b) is same, the degree of hydrogen of ions can't be same. To explain why we assume that degree of hydrolysis of cation and anion is same, we needed to now look at the third reaction i.e.,combination of H^(+) and OH^(-) ions. It is obvious that this reaction happens only because one reaction produced H^(+) ion and the other prodcued OH^(-) ions. We can also note that this reaction causes both the hydrolysis reaction to occur more since their product ions are being consumed. Keep this in mind that the equilibrium which has smaller value of the equilibrium constant is affected more by the common ion effect. For the same reason if for any reson a reaction is made to occur to a greater extent by the consumption of any of the prodcut ion, the reaction with the smaller value of equilibrium constant tends to get affected more. Therefore, we conclude that firstly the hydroylsis of both the ions occurs more in the presence of each other (due to consumption of the product ions) than in each other's absence. Secondly,the hydroylsis of the ion which occurs to a lesser extent (due to smaller value of K_(h)) is affected more than the one whole K_(h) is greater. Hence we can see that the degree of hydroylsis of both the ions would be close to each other when they are getting hyderolysed in the presence of each other. For 0.1 M CH_3COONH_(4) salt solution given, K_(a)(CH_(3)COOH)=K_(b)(NH_(4)OH)=2xx10^(-5) . In the case : degree of hydrolysis of cation and anion are :
Eight small drops, each of radius r and having same charge q are combined to form a big drop. The ratio between the potentials of the bigger drop and the smaller drop is
Nucleophilic substitution reactions generally expressed as Nu^(-) +R-L rarr R-Nu +L^(-) Where Nu^(-) rarr Nucleophile , R-L rarr substrate, L rarr leaving group The best leaving groups are those that become the most stable ions after they depart. since most leaving group leave as a negatibe ion, the best leaving groups are those ions that stabilize a negative charge most effectively. A good leaving group should be (a) electron-withdrawing to polarize the carbon (b) stable once it has left (not a strong base) (c) polaristable to maintain partial bonding with the carbon in the transition state (both S_(N)1 and S_(N)2) . This bonding helps to stabilise the transition state and reduces the activation energy. (I) CH_(3)Br (II) CH_(3)F (III) CH_(3)OH (IV) CH_(3)OSO_(2)CF_(3) The correct order of decreasing reactivity of the above compounds towards CH_(3)O^(-) in an S_(N)2 reaction is:
Recommended Questions
- (A) With HBr, anisole forms bromobenzene and methyl alcohol. (R ) Br...
Text Solution
|
- Steric Hindrance
Text Solution
|
- STERIC HINDRANCE- EXAMPLES
Text Solution
|
- Statement-I, underset("Major product")(Me-overset(OH)overset(|)(C)H-un...
Text Solution
|
- Cosider the given reaction for preparation of alkyne. (Fritsch reactio...
Text Solution
|
- Cosider the given reaction for preparation of alkyne. (Fritsch reactio...
Text Solution
|
- Cosider the given reaction for preparation of alkyne. (Fritsch reactio...
Text Solution
|
- Phenyl methyl ether (on anisole) reacts with HI to give phenol and met...
Text Solution
|
- (A) With HI, anisole forms iodobenzene and methyl alcohol. (R ) I^(-...
Text Solution
|