Side-chain oxidation: (alkylbenzene test)
Alkylbenzene is easily oxidized by acidified KMnO4 or k2cr2o7. In these reactions, the alkyl groups are oxidized keeping the benzene ring intact. CH, COOH
Regardless of the length of an alkyl group, it gives only one carboxyl group. In addition, The Color of the KMnO4 is discharged. Therefore, this reaction is used as a test for alkylbenzenes. Guidance on electrophilic substitution reactions:
When an electrophilic substitution reaction occurs in the benzene ring, we get only one monosubstituted benzene because the six positions in the ring are equivalent. However, the introduction of a second group in the ring can result in three isomeric products Ortho, meta and for dissolved.
At random, 40% of Ortho, 40% meta and 20% para-dissolved products are expected. But the actual desubstitution of benzene does not follow this principle of chance. for example, m-nitrochlorobenzene is the main product of the following halogenation reaction.
This means that the group present in the monosubstituted benzene ring has the directive effect and therefore determines the position or orientation of the new input groups.
There are two types of groups.
1-ortho and para-Director Groups 2-meta-Director Groups 1. Ortho and para-director groups:
These groups release electrons to the benzene ring, thus facilitating the availability of electrons to electrophiles at the ortho and para positions.
This results in an increased chemical reactivity of the benzene ring to electrophiles. The benzene ring can offer more than one position (ortho and para) for new input groups. These groups are called ortho and para leadership groups. CF, CH, CH,
The electron-releasing effect of the methyl group is significant and makes the ring a good nucleophile. Due to this increased reactivity, more nitro groups can be replaced in the benzene ring.
Target steering groups: (benzene ring deactivators)
These groups remove electrons from the benzene ring back to themselves, thereby reducing the availability of electrons for electrophiles in the ortho and para positions. This results in a decrease in the chemical activity of benzene. In addition, due to the electron withdrawal effect of these substituents, the ortho and para positions become more electron deficient than the target position. Thus, the input electrophile will prefer to attack in the target position rather than in the ortho and para positions. These groups are called meta-direction groups, for example.
Mechanism of nucleophilic substitution reactions:
Alkyl halides can undergo nucleophilic substitution reactions in two different ways:
1. Bimolecular nucleophilic substitution (SN2) (occurs in one step)
2. Unimolecular nucleophilic substitution (SN1) (occurs in two stages)
Nucleophilic substitution reactions in alkyl halides involve two main processes.
1. C-L / C-X connection breakage
2. Formation of a C-Nu bond
The mechanism of nucleophilic substitution reactions depends on the time of these two processes.
* If the two processes occur simultaneously, the mechanism is called SN2.
• If the link breaks first, followed by the formation of a new link, the mechanism is called SN1.
I-bimolecular nucleophilic substitution (SN2)
One mechanism in which the arrival and departure of Nucleophiles occurs simultaneously is the SN2 mechanism.
* It is a one-step mechanism.
* Primary alkyl halides provide this reaction.
As soon as the nucleophile begins to attack the electrophilic carbon of the substrate, the bond with which the output group is attached begins to break. In other words, the extent of the formation of securities is equal to the extent of the breakdown of securities. This is called the transition state.
2. Nucleophile attack direction:
The important feature of this mechanism is the direction of attack of the attack nucleophile. He attacks from the opposite side of the initial group. This rear attack is possible due to the smaller volume around the electrophilic carbon.
3. Hybridization variation:
In order to give enough space for the nucleophile to attack, the substrate carbon atom changes its hybridization state from tetrahedral sp3 to planar sp2. Note: nucleophile attack, change in hybridization state and