Draw Newman and Sawhorse projections for the eclipsed and staggered conformations of ethane. Which of these conformations is more stable and why? .
In staggered form of ethane, the electron clouds of carbon-hydrogen bonds are as far apart as possible. Thus, there are minimum repulsive forces, minimum energy and maximum stability of the molecule. On the other hand, when the staggered form changes into the eclipsed form, the electron clouds of the carbon-hydrogen bonds come closer to each other resulting in increase in electron cloud repulsions. To check the increased repulsive forces, molecule will have to possess more energy and thus has lesser stability.
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?
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
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.
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
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
Arrange the following: HCl, HBr, HI, HF in order of decreasing reactivity towards alkenes.
What happens when benzene is treated with excess of Cl2 in presence of sunlight? Give chemical reaction.
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?
(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.
Write down the products ofozonolysis ofl, 2-dimethylbenzene (o-xylene). How does the result support Kekule structure of benzene?
Why does benzene undergo electrophilic substitution reactions easily and nucleophilic substitutions with difficulty?
Suggest the name of another Lewis acid instead of anhydrous aluminium chloride which can be used during ethylation of benzene.
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
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
An alkene ‘A’ contains three C—C, eight C—H, a-bonds, and one C—C n-bond. ‘A’ on ozonolysis gives two moles of an aldehyde of molar mass 44 u. Write the IUPAC name of’A’.
Draw the cis- and trans-structures for hex-2-ene. Which iosmer will have higher b.p. and why?
Arrange benzene, n-hexane and ethyne in decreasing order of acidic behaviour. Also give reason for this behaviour.
