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![[Post New]](/templates/default/images/icon_minipost_new.gif) 25 Jun 2008 21:29:07 IST
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i want to know about resonance, inductive effect,hyperconjugation
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25 Jun 2008 22:05:48 IST
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Inductive effect - effect of electronegativity, transmitted through intermediate sigma bonds. For example, chloroacetic acid is stronger than acetic acid, because the electron pulling effect of Cl stabilises the accumulation of negative charge on the anion.
Mesomeric effect - effect of resonance, transmitted through conjugated bonds. For example, the OH group of a phenol is strongly activating and ortho, para - directing towards electrophilic substitution in a benzene ring because of the interaction between oxygen lone pairs and the ring; you can write valence structures with a double bond between O and C, a positive charge on O, and a negative charge on the ortho or para ring carbon.
Hyperconjugation - this is a suggested special kind of mesomeric effect, involving for example hydrogen atoms on the -CH3 group of toluene, and suggested contributions from valence structures in which one of these H is H+, and again there is a double bond between the carbon of the CH3 group and the ring, and a negative charge distributed over ortho and para ring carbons. This was suggested to explain the fact that -CH3 is more strongly activating than -C(CH3)3 towards electrophilic attack.
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The Scientist does not study nature because it is useful; he studies it because he delights in it, & he delights in it because it is beautiful. If nature were not beautiful, it would not be worth knowing, life would not be worth living. Ofcourse I do not here speak of that beauty that strikes the senses, the beauty of qualities & appearances; not that I undervalue such beauty, far from it, but it has nothing to do with science; I mean that profounder beauty which comes from the harmoniuos order of the parts, & which a pure intelligence can grasp. |
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25 Jun 2008 22:06:41 IST
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Also check
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The Scientist does not study nature because it is useful; he studies it because he delights in it, & he delights in it because it is beautiful. If nature were not beautiful, it would not be worth knowing, life would not be worth living. Ofcourse I do not here speak of that beauty that strikes the senses, the beauty of qualities & appearances; not that I undervalue such beauty, far from it, but it has nothing to do with science; I mean that profounder beauty which comes from the harmoniuos order of the parts, & which a pure intelligence can grasp. |
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