Organic Chemistry - Some Basic Principles and Tech

  (a) They are structural isomers. The given compounds have the same molecular formula but they differ in the position of the functional group (here ketone group: first one at C-3 and second one at C-2 positions).

(b) They are geometrical isomers. Compounds having the same molecular formula, the same constitution, and the sequence of covalent bonds, but with the different relative position of their atoms in space are called geometrical isomers.

(c) They are resonance contributors because they differ in the position of electrons but not atoms.

(a) Nucleophilic substitution (b) Electrophilic addition
(c) Bimolecular elimination (d) Nucleophilic substitution with rearrangement.

(a) Here, HO^– acts as a nucleophile as it is an electron-rich species, i.e., it is a nucleus-seeking species.

(b) Here, –CN acts as a nucleophile as it is an electron-rich species, i.e., it is a nucleus-seeking species.

(c) CH₃C⁺O acts as an electrophile as it is an electron deficient species.

Electrophiles: The name electrophiles mean electron loving. Electrophiles are electron deficient. They may be positive ions or neutral molecules.
Ex: H⁺, Cl⁺, Br⁺, NO₂⁺, R₃C⁺, RN₂⁺, AlCl₃, BF₃
Nucleophiles: The name nucleophiles means 'nucleus loving' and indicates that it attacks the region of low electron density (positive centres) in a substrate molecule. They are electron rich they may be negative ions or neutral molecules.
Ex: Cl^– Br^–, CN^–, OH^–, RCR₂^–, NH₃, RNH₂, H₂O, ROH etc.

Due to hyperconjugation, alkyl groups act as electron donors when attached to a π - system as shown below:

Nitroethoxide ion (O₂NCH₂CH₂O^–) is more stable than ethoxide ion (CH₃CH₂O^–) due to -I effect of nitro group which decreases the negative charge of oxide ion of nitroethoxide ion leading to stability. In contrast, CH₃CH₂ has +I-effect. It, therefore, tends to intensify the -ve charge and hence destabilizes it.

(a) H-COOH

CH₃—COOH
CH₃CH₂—COOH

CH₃CH₂CH₂—COOH
CH₃CH₂CH₂CH₂—COOH

(b) CH₃COCH₃
CH₃COCH₂CH₃
CH₃COCH₂CH₂CH₃
CH₃COCH₂CH₂CH₂CH₃
CH₃CO (CH₃)₄CH₃

(c) H—CH=CH₂
CH₃CH=CH₂

CH₃CH₂CH=CH₂
CH₃CH₂CH₂CH=CH₂
CH₃CH₂CH₂CH₂CH=CH₂

(a) 2, 2-Demethylpentane

(b) 2, 4, 7-Trimethyloctane. For two alkyl groups on the same carbon its locant is repeated twice, 2, 4, 7-locant set is lower than 2, 5, 7.
(c) 2- Chloro-4-methylpentane. Alphabetical order of substituents, (d) But-3-yn-1-ol. Lower locant for the principal functional group, i.e., alcohol.