Resonance explains the stability of aromatic compounds, some unusual bond lengths in some molecules, behaviour of `o- and p` directing and m-directing groups

Stability of alkenes, carbocations, alkyl free radicals, orienting effect of alkyl groups in aromatic ring, unexpected bond lengths in some molecules, etc. can be explained by hyperconjugation

The typical reaction of benzene and other aromatic compounds is electrophilic substitution. Presence of electron donating group activates the ring towards electrophilic substitution, while presence of electron withdrawing group deactivates the ring towards electrophilic substitution but at the same time activates the ring towards nucleophilic substitution. Some groups are predominantly meta directing and all of these are deactivating. Except halogen, most of the o- and p- directing groups are activating groups. (E.A.S = Electrophilic aromatic substation) Presence of nitro group in benzene ring:

The typical reaction of benzene and other aromatic compounds is electrophilic substitution. Presence of electron donating group activates the ring towards electrophilic substitution, while presence of electron withdrawing group deactivates the ring towards electrophilic substitution but at the same time activates the ring towards nucleophilic substitution. Some groups are predominantly meta directing and all of these are deactivating. Except halogen, most of the o- and p- directing groups are activating groups. (E.A.S = Electrophilic aromatic substation) The reaction of toluene with Cl_2 in presence of FeCl_3 gives predominantly:

Bond Length: Internuclear distance between two adjacent atoms in an species is known as bond length, -Bond length depends on: i) size of the atom involved in the bond formation ii) size of the orbitals involved in the bond formation iii) Lone pair-long pair repulsion iv) Resonance v) s-character of combining orbitals with the increasing size of the atoms and atomic orbitals bond length increases. Lone pair-lone pair repulsion increases bond length (if atoms are small sized) whereas resonance can increase some bond lengths and decrease some other bond length. With increasing s-character bond length decreases, whereas with increasing multiplicity of bonds, bond length decreases. However, in some cases, bond lengths are also affected by relative position of bonds (between two similar atoms). Usually but not always with increasing bond length, bond strength (and hence bond dissociation energy) decreases. The correct order of B-F bond length follows the sequence

How many of the following statements is (are) true about resonance. a) Resonance is an intramolecular process. b) Resonance involves delocalization both of s and p electrons. c) Resonance involves delocalization of pi electrons only. d) Resonance decreases potential energy of a molecule. e) Resonance has no effect on the potential energy of a molecule. f) Resonance is the only way to increase molecular stability. g) Resonance is not the only way to increase molecular stability. h) Any resonating molecule is always more stable than any nonresonating molecule. i) The canonical struture explains all features of a molecule. j) The resonance hybrid explains all features of a molecule. k) Resonating structures are real and resonance hybrid is imaginary. l) Resonance hybrid is real and resonating structures are imaginary. m) Resonance hybrid is always more stable than all canonical structures.

Bond Length: Internuclear distance between two adjacent atoms in an species is known as bond length, -Bond length depends on: i) size of the atom involved in the bond formation ii) size of the orbitals involved in the bond formation iii) Lone pair-long pair repulsion iv) Resonance v) s-character of combining orbitals with the increasing size of the atoms and atomic orbitals bond length increases. Lone pair-lone pair repulsion increases bond length (if atoms are small sized) whereas resonance can increase some bond lengths and decrease some other bond length. With increasing s-character bond length decreases, whereas with increasing multiplicity of bonds, bond length decreases. However, in some cases, bond lengths are also affected by relative position of bonds (between two similar atoms). Usually but not always with increasing bond length, bond strength (and hence bond dissociation energy) decreases. In which of the following all bonds are not equivalent?

Tautomerism is due to spontaneous interconversion of two isomeric forms with differentfunctional groups into each other. The term tautomer means constitutional isomers thatundergo such rapid inter conversion that they cannot be independently isolated. In keto-enol tautomerism although Keto form in general is more stable, but some factors like H-bonding and extended double bonds conjugation may increase the stability of enol form Enolic form of acetyl acelone is stabilized due to (I) resonance as a result of conjugation (II) intra molecular H-bonding (III) dipole- dipole repulsion

Block of mass 'm' is sliding up on the smooth incline plane, with some constant velocity. Now, on the block match the magnitude value of the forces on 'm' in the given directions take the components of all the forces in the given direction) {:("Column - I","Column -II"),("A) Net force component is horizontal direction ","P) zero"),("B) Net - force compnent in vertical direction", "Q) " mg sin theta cos theta),("C) Net force component along the incline plane ","R)" mg sin theta),("D) Net force component perpendicular to the incline plane ","S) " mg (1-cos^(2) theta)):}

Hyperconjugation describes the orbital interactions between the p-systems and the adjacent s-bond of the substituent group(s) in organic compounds. Hyperconjugation is also called as Baker and Nathen effect. The necessary and sufficient condition for the hyperconjugation are : i) Compound should have at least on sp2 hybrid carbon of either alkene, carbocation or alkyl free radical. ii) A-carbon with respect to sp2 hybrid carbon should have at least one hydrogen. Hyperconjugation are of three types: (i) s(C-H), p-conjugation. (iii) s(C-H), positive charge conjugation iv) s(C-H), odd electron conjugation The hyperconjugation may be represented as Number of resonating structures due to hyperconjugation = (n + 1) where n is the number of a-hydrogen. Greater is the number of such forms, more is the stability of the species under considersation. Stability of saturated alkyl carbocations can be explained by