(i) State the necessary compound to be aromatic according to Huckel’s rule.
(ii) Explain why alkyl groups act as electron donors when attached to a `pi` system.

Explain why alky1 groups act as electron donors when attacted to a pi-system .

What are the conditions for a compound / species to be aromatic according to Huckel 's rule ?

According to Huckel’s rule an aromatic compound must possess

Complex compounds are molecular compounds which retain their identities even when dissolved in water. They do not give all the simple ions in solution but instead furnish complex ions. The complex compounds are often called coordination compounds because certain groups called ligands are attached to the central metal ion by coordinate or dative bonds. coordination compounds exhibit isomerism, both structural and stereoisomerism. the structure, magnetic property, colour and electrical properties of complexes are explained by various theories: Q. Arrange the following compounds in order of their molar conductance: (i) K[Co(NO_(2))_(4)(NH_(3))_(2)] (ii) [Cr(ONO)_(3)(NH_(3))_(2)] (iii) [Cr(NO_(2))(NH_(3))_(5)]_(3)[Co(NO_(2))_(6)]_(2) (iv) Mg[Cr(NO_(2))_(5)(NH_(3))]

Complex compound are molecular compounds which rectain their identities even when dissolved in water. They do not give all the simple ions in solution but instead furnish complex ions with complicated structures. The complex compounds are often called coordination compounds because certain groups called ligands are attached to the central metal ion by coordinate or dative bonds. Coordination compounds exhibit isomerism, both structural and stereoisomerism. The structure, magnetic property, colour and electrical properties of complexes are explained by various theories. Arrange the following compounds in order of their Molar conductance : (P) K[Co(NO_(2))_(4)(NH_(3))_(4)(NH_(3))_(2)]" " (Q) [Cr(ONO)_(3)(NH_(3))_(3)] (R ) [Cr(NO_(2))(NH_(3))_(5)]_(3)[Co(NO_(2))_(6)]_(2) (S) Mg[Cr(NO_(2))_(5)(NH_(3))]

The high reactivity of alkyl halides can be explained in tems of nature of C-X bond which is highly polarised covalent bond due to large difference in the electronegativities of carbon and halogen atom. This polarity is responsible for the nucleophilic substitution reaction of alkyl halides which mostly occur by S_(N^(1)) and S_(N^(2)) mechanisms. S_(N^(1)) reaction is a two step process and in the first step R-X ionises to give carbocation (slow process). In the second step the nucleophilic attacks the carbocation from either side to form the prodcut (fast process) . In S_(N^(1)) reaction there can be reacemization and inversion . S_(N^(1)) reaction is favoured by heavy (bulky) groups on the carbon atom attached to halogens. i.e., R_(3)C-Xgt R_(2)CH-Xgt R_CH_(2)X gt CH_(3)X. " In " S_(N^(2)) reaction the strong nucleophilie OH^(-) attacks from the opposite side of the chlorine atom to give an inyermediate (transition state). which breaks to yield the product (alcohol) and leaving (X^(-)) group. The alcohol has a configuration opposite to that of the bromide and is said to proceed with inversion of configuration. S_(N^(2)) reaction is favoured by small groups on the carbon atom attached to halogen i.e., CH_(3)-X gt R-CH_(2)X gt R_(2) CHX gt R_(3) C-X S_(N^(1)) reaction of optically active alkyl halide leads to :