Why is benzene extra-ordinarily stable though it contains three double bonds?
The six electrons of the p-orbitals cover all the six carbon atoms, and are said to be delocalized. As a result of delocalization there formed a stronger n-bond and a more stable molecule.
In the alkane, CH3CH2—C(CH3)2—CH2—CH(CH3)2, identify 1 °, 2 °, 3 ° carbon atoms and give the number of H-atoms bonded to each one of these.
Nucleophiles and electrophiles are reaction intermediates having electron rich and electron deficient centres respectively. Hence, they tend to attack electron deficient and electron rich centres respectively. Classify the following species as electrophiles and nucleophiles.
For the following compounds, write structural formulas and IUPAC names for all possible isomers having the number of double or triple bond as indicated:
(a) C4H8 (one double bond) (b) C5H8 (one triple bond)
The relative reactivity of 1 °, 2 ° and 3 ° hydrogens towards chlorination is 1: 3.8 : 5. Calculate the percentages of all monochlorinated products obtained from 2-methylbutane.
Which of the following are correct?
(a) CH3 – O – CH+2 is more stable than CH3 – CH+2
(b) (CH3)2CH+ is less stable than CH3 – CH2 – CH+2
(c) CH2 = CH – CH+2 is more stable than CH3 – CH2 – CH+2
(d) CH2 = CH+ is more stable than CH3 – CH+2
Out of benzene, m-dinitrobenzene and toluene which will undergo nitration most easily and why?
The molecules having dipole moment are________ .
(a) 2,2-Dimethylpropane
(b) trans-Pent-2-ene
(c) cw-Hex-3-ene
(d) 2,2,3,3-Tetramethylbutane
Arrange the following: HCl, HBr, HI, HF in order of decreasing reactivity towards alkenes.
Write the IUPAC names of the following compounds.
(i) (CH3)CCH2C(CH3)3 (ii) (CH3)2C(C2H5)2
Explain the term aromaticity. What are the necessary conditions for any compound to show aromaticity?
(a) Why are alkenes called unsaturated hydrocarbons?
(b) How will you test the presence of double bond in an alkene?
(c) Name the products formed when propene is subjected to ozonolysis.
Propanal and pentan-3-ene are the ozonolysis products of an alkene. What is the structural formula of the alkene?
Draw the cis- and trans-structures for hex-2-ene. Which iosmer will have higher b.p. and why?
Why does benzene undergo electrophilic substitution reactions easily and nucleophilic substitutions with difficulty?
How will you demonstrate that double bonds of benzene are somewhat different from that of olefins?
In an electrophilic substitution reaction of nitrobenzene, the presence of nitro group ________ ‘
(a) deactivates the ring by inductive effect
(b) activates the ring by inductive effect
(c) decreases the charge density at ortho- and para-positions of the ring relative to meta-position by resonance
(d) increases the charge density at meta-position relative to the ortho and para-positions of the ring by resonance
Alkynes on reduction with sodium in liquid ammonia form trans alkenes. Will butene formed on the reduction of but-2-yne show geometrical isomerism?
Rotation around carbon-carbon single bond of ethane is not completely free. Justify the statement.
An alkene ‘A’ on ozonolysis gives a mixture of ethanal and pentan-3-one. Write the structure and IUPAC name of ‘A’.
Suggest the name of another Lewis acid instead of anhydrous aluminium chloride which can be used during ethylation of benzene.
What happens when benzene is treated with excess of Cl2 in presence of sunlight? Give chemical reaction.
Discuss the preparation of alkanes by Wurtz reaction. What is the limitaHon of the reaction?
Arrange the following carbanions in order of their decreasing stability.
(A) H3C-C ≡ C–
(B) H-C ≡ C–
(C) H3C – CH–2
(a) A>B>C
(b) B>A>C
(c) C>B>A
(d) C>A>B
Draw Newman and Sawhorse projections for the eclipsed and staggered conformations of ethane. Which of these conformations is more stable and why? .
