Organic Chemistry: SN2 Reactions and Halides

Sulphuric acid cannot be used in reactions with alcohols because it is a strong oxidizing agent.

Alkyl halides, though polar, are immiscible with water due to the energy needed to break the strong hydrogen bonds in water while forming weaker attractions with the halide. This energy trade-off makes dissolving unfavorable.

KCN is ionic, providing cyanide ions where carbon is the primary attack site due to forming a stronger C-C bond. AgCN is mainly covalent, leaving nitrogen free to donate electrons, leading to isocyanide formation.

Primary halides (1o) undergo SN2 reactions faster due to less steric hindrance, allowing for easier nucleophilic attack. The order of reactivity is 1o > 2o > 3o.

Iodine is a better leaving group than chlorine due to its larger size, making it easier to detach from the molecule in SN2 reactions.

Grignard reagents are highly reactive and react with any source of proton, such as water, forming hydrocarbons. This reactivity requires anhydrous conditions to prevent undesirable side reactions.

The positive charge is dispersed through the molecule, making it more stable. This occurs when a carbocation is adjacent to a benzene ring.

Alkyl chlorides in aqueous KOH undergo nucleophilic substitution. OH- acts as a nucleophile due to its hydration and reduced basicity.

Alkyl chlorides with alcoholic KOH undergo elimination. Alkoxide ions (RO-) are strong bases, favoring the removal of HX to form an alkene.

The lone pair of electrons on the halogen atom is in conjugation with the pi electrons of the benzene ring. This causes partial double bond character in the C-Cl bond, leading to a decrease in bond length and reactivity.

Due to the resonance stabilization of the allylic carbocation, allylic halides exhibit higher reactivity in the SN1 reaction.

Dipole moment is a measure of the polarity of a molecule. It increases when the difference in electronegativity between the atoms involved in the bond is greater. This is because a larger difference in electronegativity creates a larger separation of charge.

The C-Cl bond in chlorobenzene has a partial double bond character due to the conjugation of the lone pair of electrons on chlorine with the pi electrons of the benzene ring. This causes a decrease in bond length and thereby a decrease in the dipole moment.

The symmetry of the p-chloro benzene molecule allows it to fit into the crystal lattice more easily. This leads to greater intermolecular forces and a higher melting point compared to its ortho and meta isomers.

Alcohols form hydrogen bonds with water molecules, creating a strong attractive force that allows them to dissolve.

The -OH group in phenol is attached to a more electronegative sp2 hybridized carbon, leading to a more polarized O-H bond and easier ionization. This makes phenol more acidic than alcohols.

Phenoxide ion's negative charge is delocalized through resonance, increasing its stability. Alkoxide ion's negative charge is localized on oxygen, making it less stable.

Nitro groups withdraw electron density, increasing the polarity of the O-H bond and making the proton easier to release. Methoxy groups donate electron density, decreasing polarity and making the proton harder to release.

Ortho-nitrophenol forms an intramolecular hydrogen bond, preventing association and allowing for easy vaporization. Para-nitrophenol forms intermolecular hydrogen bonds, causing association and hindering vaporization.

The lone pair of electrons on the -OH group participates in resonance with the benzene ring's pi electrons, increasing electron density in the ring and making it more susceptible to electrophilic attack.

Phenol reacts with active metals like sodium and potassium, producing phenoxide and hydrogen gas. It also reacts with aqueous sodium hydroxide to form sodium phenoxide and water.

Cyclohexanone forms cyanohydrin readily because it lacks steric hindrance around the carbonyl group, allowing the cyanide ion to easily attack.

Semicarbazide has two amino groups, but only one participates in forming semicarbazones. The other amino group is involved in resonance, reducing its electron density and making it a poor nucleophile.

Ester formation from carboxylic acids and alcohols is reversible. Removing water or the ester as it forms shifts the equilibrium towards product formation, increasing the yield of ester.

Ammonolysis produces a mixture of primary, secondary, tertiary amines, and quaternary ammonium salts. This lack of control makes it less desirable for specific amine synthesis.

Aryl halides like those in aniline don't undergo nucleophilic substitution easily due to their stability. Therefore, aniline cannot be made by the Gabriel phthalimide synthesis, which relies on this reaction.

Alkyl amines are stronger bases than ammonia due to the +I effect of the alkyl group. This effect pushes electron density towards the nitrogen, increasing its availability for protonation.

Aniline is less basic than ammonia because the lone pair of electrons on the nitrogen atom in aniline participates in resonance with the aromatic ring. This delocalization reduces electron density on the nitrogen, making it less available for protonation.

The lone pair on nitrogen in aniline is involved in resonance with the aromatic ring, making it less available for protonation.

The anilinium ion formed by protonation has only two resonance structures, while neutral aniline has more, making aniline more stable than its protonated form.

Tertiary amines have the strongest +I effect due to three alkyl groups, increasing electron density and promoting protonation.

The combination of +I effect, hydration, and steric effects dictates the basicity order in solution. In methyl amines, hydrogen bonding dominates, making secondary amines the most basic.

In ethyl amines, steric hindrance to hydrogen bonding is significant, making the +I effect more important, resulting in a different basicity order: secondary amines are most basic.

Aniline reacts with AlCl3 to form a salt, where nitrogen gains a positive charge, making it a strong deactivating group that prevents Friedel-Crafts reactions.

Diazonium salts allow for the replacement of the diazo group with other functional groups, enabling the synthesis of a wide range of substituted aromatic compounds.

Diazonium salts serve as valuable intermediates for preparing substituted aromatic compounds that are challenging to obtain through direct substitution.

Electron density increases at the ortho and para positions of a benzene ring due to resonance effects. This makes these positions more susceptible to electrophilic attack.

Ethanol can form hydrogen bonds between molecules due to the presence of the -OH group, while methoxymethane cannot. Hydrogen bonds are stronger than the van der Waals forces present in methoxymethane, resulting in a higher boiling point for ethanol.

Williamson synthesis involves an SN2 reaction with an alkoxide and an alkyl halide. Tertiary alkyl halides undergo elimination reactions, leading to alkene formation instead of ethers. Aryl and vinyl halides are unreactive in SN2 reactions due to their low reactivity.

Benzaldehyde is less reactive than propanal in nucleophilic addition reactions because the carbonyl group in benzaldehyde is less electrophilic. This is due to resonance delocalization of electrons in the benzene ring, which reduces the polarity of the carbonyl group.

Aldehydes are more reactive than ketones in nucleophilic addition reactions because the carbonyl carbon in aldehydes is more electrophilic. This is due to both steric and electronic factors. Sterically, ketones have more bulky groups around the carbonyl group, hindering nucleophilic attack. Electronically, the alkyl groups in ketones are electron donating, making the carbonyl group less electrophilic.

Carboxylic acids are stronger acids than phenols because the carboxylate ion is more stable than the phenoxide ion. The stability of the carboxylate ion is due to the delocalization of negative charge over two equivalent oxygen atoms, while the phenoxide ion has an uneven charge distribution. The negative charge on the carboxylate ion is also on a more electronegative oxygen atom, leading to greater stability.

The presence of three methyl groups at the α-positions of 2,2,6-trimethylcyclohexanone causes steric hindrance, preventing the nucleophilic attack of the cyanide ion. This steric hindrance does not exist in cyclohexanone, allowing for efficient cyanohydrin formation.