Chapter4- Aromatic Compounds- Pharmacgy

The compound is named 3-ethylphenol because it has an ethyl group attached to the third carbon atom of the phenol ring. The numbering of the carbon atoms in the phenol ring starts from the carbon atom attached to the hydroxyl group, and the ethyl group is attached to the third carbon atom. Therefore, the correct name for this compound is 3-ethylphenol.

Aromatics are compounds that contain a benzene ring, which is highly stable and does not readily undergo addition or elimination reactions. Oxidation reactions typically involve the addition of oxygen or the removal of hydrogen, which is not commonly observed in reactions involving aromatics. Substitution reactions, on the other hand, involve the replacement of one atom or group with another, and this is the most common type of reaction observed with aromatics. Therefore, the correct answer is substitution.

In the bromination of benzene, the reagent used is Br2. This is because bromine (Br2) is a strong electrophile and can easily react with benzene to substitute one of its hydrogen atoms with a bromine atom. The reaction is typically carried out in the presence of a catalyst such as FeBr3 or AlBr3 to facilitate the reaction. HNO3 and H2SO4 are not used as reagents in the bromination of benzene.

FeCl3 acts as a catalyst in the chlorination of benzene. A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process. In this reaction, FeCl3 facilitates the formation of the electrophilic species, which is necessary for the substitution of a hydrogen atom on the benzene ring with a chlorine atom. The FeCl3 helps in the generation of the electrophile by accepting a lone pair of electrons from chlorine, making it more reactive. Therefore, FeCl3 plays a crucial role in speeding up the reaction without undergoing any permanent changes itself.

The correct answer is "We start by bromination and then nitration". This is because bromination is typically performed before nitration in organic synthesis reactions. Bromination involves adding a bromine atom to a molecule, while nitration involves adding a nitro group (NO2) to a molecule. Performing bromination first ensures that the bromine atom is added to the correct position on the benzene ring before the nitro group is added.

The correct answer for the reagent and catalyst used for the nitration of benzene is HNO3 /H2SO4. In this reaction, nitric acid (HNO3) acts as the reagent, providing the nitro group (NO2+) required for the nitration process. Meanwhile, sulfuric acid (H2SO4) acts as the catalyst, facilitating the reaction by increasing the acidity of the reaction medium and generating the necessary electrophile for the substitution reaction. Together, these reagent and catalyst ensure the successful nitration of benzene.

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The given answer, P-phenylstyrene, correctly names the structure. P-phenylstyrene refers to a compound with a phenyl group (C6H5) attached to the para position (P) of a styrene molecule. Styrene is a compound with a vinyl group (C6H5CH=CH2) attached to a benzene ring. Therefore, P-phenylstyrene accurately describes the structure of the compound.

The correct answer suggests that the synthesis of p-nitroethylbenzene should begin by adding the ethyl group first, followed by nitration. This sequence of reactions is likely to be more favorable because adding the ethyl group to the starting material before nitration ensures that the ethyl group is attached to the correct position on the benzene ring. Nitration can then be carried out on the ethyl-substituted benzene to introduce the nitro group at the desired position.

In isopropyl benzene, the isopropyl group is an activator and o,p-director. This means that the isopropyl group activates the benzene ring towards electrophilic substitution reactions and directs incoming substituents to the ortho and para positions.

The group -NH2 is ortho-para directing because it contains a lone pair of electrons on the nitrogen atom. This lone pair can interact with the benzene ring through resonance, stabilizing the intermediate carbocation formed during electrophilic aromatic substitution reactions. This interaction allows substitution to occur at the ortho or para positions relative to the -NH2 group, making it ortho-para directing.

The suitable set of reagents needed to carry out the transformation is CH3CH2Cl/AlCl3. This is because AlCl3 is a Lewis acid catalyst that can facilitate the formation of a carbocation intermediate. The CH3CH2Cl reagent serves as the substrate for the reaction, and under the influence of AlCl3, it can undergo a substitution reaction to form a new compound. The other reagents listed do not have the same functional group or structure as CH3CH2Cl, and therefore would not be suitable for the transformation.

Carbon atom 4 will have the highest reactivity toward nitration because it is attached to a methyl group (-CH3) and a chlorine atom (-Cl). The presence of these electron-withdrawing groups increases the electron deficiency on the carbon atom, making it more susceptible to attack by the nitration reagent. The methyl group and chlorine atom both have a greater electron-withdrawing effect compared to the other carbon atoms, thus enhancing the reactivity of carbon atom 4.

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The step from A to C is considered the slowest because it is the longest distance to travel compared to the other options.

In sulfonation, the electrophile is a species that is electron-deficient and seeks to attract electrons. Among the given options, HSO3+ is the only species that fits this description. HSO3+ is a positively charged species, indicating that it has an electron deficiency and can act as an electrophile. The other options, HSO4-, HSO3-, and SO3, are either negatively charged or neutral, and therefore do not possess the electron deficiency required to be an electrophile in sulfonation reactions.

The compound 2,3,4,5-tetrabromo cumene is named based on the number and position of the bromine atoms and the parent hydrocarbon. The prefix "2,3,4,5-tetrabromo" indicates that there are four bromine atoms attached to the cumene molecule. Cumene is a common name for isopropylbenzene, which consists of a benzene ring with an isopropyl group attached. Therefore, the correct name for the compound is 2,3,4,5-tetrabromo cumene.

In the Fridel-Craft acylation reaction, the catalyst used is AlCl3. This catalyst is essential for the reaction as it helps in activating the acyl chloride, allowing it to react with the aromatic compound. AlCl3 acts as a Lewis acid, accepting a lone pair of electrons from the acyl chloride and forming a complex. This complex then reacts with the aromatic compound, leading to the formation of the acylated product. FeCl3 is not a suitable catalyst for this reaction, as it does not provide the necessary activation for the acyl chloride. H2SO4 is also not a catalyst for Fridel-Craft acylation.

The correct answer is CH3CH2COCl/AlCl3. This is because the reagents CH3CH2COCl and AlCl3 are commonly used in the Friedel-Crafts acylation reaction, which is a method for introducing an acyl group (RCO-) onto an aromatic ring. In this case, the acyl group is CH3CH2CO-. The reaction is typically carried out in the presence of a Lewis acid catalyst, such as AlCl3, which helps to activate the acyl chloride and facilitate the reaction with the benzene molecule.

The most stable intermediate is B.

The correct answer is 3>2>1>4. In electrophilic aromatic substitution reactions, the reactivity of compounds is determined by the presence of electron-donating or electron-withdrawing groups on the aromatic ring. Compound 3 is the most reactive because it has a strong electron-donating group (such as an amino group) that increases the electron density on the ring, making it more susceptible to attack by electrophiles. Compound 2 is less reactive because it has a moderately electron-donating group (such as a methyl group) that still increases the electron density but to a lesser extent. Compound 1 is less reactive than 2 because it has a weak electron-donating group (such as an alkyl group) that only slightly increases the electron density. Compound 4 is the least reactive because it has a strong electron-withdrawing group (such as a nitro group) that decreases the electron density on the ring, making it less susceptible to attack by electrophiles.

The given answer suggests that intermediate 4 is the most stable, followed by intermediate 1, then intermediate 2, and finally intermediate 3. This ranking is based on the stability of the intermediates, with intermediate 4 being the most stable and intermediate 3 being the least stable.

The correct answer is 3>1>2. This is because chlorobenzene is less reactive towards electrophilic substitution compared to o-dichlorobenzene and benzene. The presence of electron-withdrawing chlorine atoms in o-dichlorobenzene increases its reactivity, making it more reactive than chlorobenzene. Benzene, being the most electron-rich compound among the three, is the most reactive towards electrophilic substitution.

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