Organic Chemistry Important Explanations
Organic Explanations
| S.No | |
| 1 | Bond enthalpy decreases as: CH3-F > CH3-Cl > CH3-Br > CH3-I |
| Because the C-X bond length increases from F to I due to the greater size. | |
| 2 | Phenol cannot be converted into chlorobenzene by using HCl |
| Because the C-O bond in phenol has partial double bond character, and the OH group is attached to a sp2 carbon | |
| 3 | Thionyl chloride is preferred to convert ROH into RCl |
| Because the side products are gases, and the product can be obtained as pure | |
| 4 | 30 alcohols can easily be converted into alkyl halides |
| Because 30 carbocations are stable | |
| 5 | Benzene is converted into iodo-benzene in the presence of an oxidizing agent like HNO3 or HIO3 |
|
C6H6 + I2/Fe ↔ C6H5I + HI Because HNO3 or HIO3 oxidises HI and prevents the backward reaction |
Organic Explanations
| 6 | ROH is converted into RI by using KI in the presence of H3PO4, not H2SO4 |
| H2SO4 converts KI into HI and then into I2 | |
| 7 | The Boiling Point of alkyl halides (RX) is higher than hydrocarbons |
| Because R-X is polar so there is dipole dipole-dipole attraction | |
| 8 | Boiling Point: R-I > R-Br > R-Cl > R-F |
| Because molecular mass decreases, so van der Waals force decreases from RI to RF | |
| 9 | Boiling Point: CH3-CH2-CH2-CH2-Br > CH3-CH2-CH(Br)-CH3 > (CH3)CBr |
| Because as the branching increases, surface area decreases, so the van der Waals force of attraction decreases | |
| 10 | p-dichlorobenzene has a higher melting point than the ortho and meta isomers |
| Because p-dichlorobenzene has a symmetrical structure so it fits well in the crystal lattice | |
| 11 | Alkyl halide (RX) with KCN gives alkyl cyanide (RCN) where whereas with AgCN it gives isocyanide (RNC) |
| KCN is ionic, and CN– is an ambident nucleophile, but it links through C because the C-C bond is more stable than C-N. On the other hand, AgCN is covalent and links through N only | |
| 12 | SN2 reactivity: CH3-X > CH3CH2-X > CH3-CH(X)-CH3 > (CH3)3C-X ( 10 >20>30) |
|
Due to steric hindrance nucleophile can not approach easily. In the SN2 path release of X and the linking of the Nucleophile take place simultaneously. |
Organic Explanations
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