Rotation around carbon-carbon single bond of ethane is not completely free. Justify the statement.
Ethane contains carbon-carbon sigma (σ) bond. Electron distribution of the sigma molecular orbital is symmetrical around the intemuclear axis of the C – C bond which is not disturbed due to rotation about its axis. This permits free rotation around aC-C single bond. However, rotation around a C – C single bond is not completely free. It is hindered by a small energy barrier due to weak repulsive interaction between the adjacent bonds. Such a type of repulsive interaction is called torsional strain. Of all the conformations of ethane, the staggered form has the least torsional strain and the eclipsed form has the maximum torsional strain. The energy difference between the two extreme forms is of the order of 12.5 kJ mol-1, which is very small. It has not been possible to separate and isolate different conformational isomers of ethane.
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.
Explain the term aromaticity. What are the necessary conditions for any compound to show aromaticity?
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
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 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
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.
Write the IUPAC names of the following compounds.
(i) (CH3)CCH2C(CH3)3 (ii) (CH3)2C(C2H5)2
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
What happens when benzene is treated with excess of Cl2 in presence of sunlight? Give chemical reaction.
Arrange the following: HCl, HBr, HI, HF in order of decreasing reactivity towards alkenes.
How will you demonstrate that double bonds of benzene are somewhat different from that of olefins?
Why does the presence of a nitro group-make the benzene ring less reactive in comparison to the unsubstituted benzene ring? Explain.
Out of benzene, m-dinitrobenzene and toluene which will undergo nitration most easily and why?
Write down the products ofozonolysis ofl, 2-dimethylbenzene (o-xylene). How does the result support Kekule structure of benzene?
Suggest the name of another Lewis acid instead of anhydrous aluminium chloride which can be used during ethylation of benzene.
(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.
Why does benzene undergo electrophilic substitution reactions easily and nucleophilic substitutions with difficulty?
Which are the correct IUPAC names of the following compound
(a) 5-(2′,2′-Dimethylpropyl)decane
(b) 4-Butyl-2,2-dimethylnonane
(c) 2,2-Dimethyl-4-pentyloctane
(d) 5-neo-Pentyldecane
Arrange the following set of compounds in order of their decreasing relative reactivity with an electrophile, E+.
(a) Chlorobenzene, 2, 4-dinitrochlorobenzene, p-nitrochlorobenzene
(b) Toluene,p—H3C—C6H4—NO2, p—O2N—C6H4—NO2.
Classify the following compounds into (i) alkanes (ii) alkenes (iii) alkynes (iv) arenes. (a) C6H6 (b) C4H8 (C) C8H8 (d) C5H8 (e) C6H14
(a) What effect the branching of an alkane has on its melting point?
(b) Which of the following has highest boiling point?
(i) 2-methyl pentane
(ii) 2, 3-diethyl butane
(iii) 2, 2-dimethyl butane
An alkene ‘A’ contains three C-C, eight C-H σ bonds and one C-C Ï€ bond. ‘A' on ozonolysis gives two moles of an aldehyde of molar mass 44 u. Deduce IUPAC name of’A’.
The intermediate carbocation formed in the reactions of HI, HBr and HC1 with propene is the same and the bond energy of HCl, HBr and HI is 430.5 kJ mol-1,363.7 kJ mol–1 and 296.8 kJ mol-1 What will be the other of reactivity of these halogen acids?
