Chemistry

Hydrocarbons

Question:

What is electrophile in sulphonation?

Answer:

SO3.

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Hydrocarbons

Q 1.

How will you distinguish between propene and propane?

Q 2.

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.
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Q 3.

Convert ethylene to ethane.

Q 4.

What happens when benzene is treated with acetyl chloride in presence of AlCl3?

Q 5.

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.

Q 6.

Discuss the shape of methane and ethane.

Q 7.

Define resonance energy. What is resonance energy of benzene?

Q 8.

What is the hybridisation of central carbon in 1,2-propadiene (CH2=C=CH2)?

Q 9.

Which of the following alkenes on ozonolysis gives a mixture of ketones only?
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Q 10.

Which type of isomerism is exhibited by but-l-yne and but-2-yne?

Q 11.

What are the necessary conditions for any system to be aromatic?

Q 12.

How will you separate propene from propyne?

Q 13.

Why do alkenes prefer to undergo electrophilic addition reaction while arenes prefer electrophilic substitution reaction? Explain.

Q 14.

What happens when ethanol is heated with cone. H2SO4?

Q 15.

Why are Alkenes called olefins?

Q 16.

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’.

Q 17.

Write the IUPAC names of the following compounds.
(i) (CH3)CCH2C(CH3)3    (ii) (CH3)2C(C2H5)2

Q 18.

What is Lindlar’s catalyst? Give its use.

Q 19.

How will you distinguish between acetylene and ethylene?

Q 20.

What are Arenes ?

Q 21.

Arrange the three isomers of pentane in increasing order of their boiling points.

Q 22.

What effect does branching of an alkane chain has on its boiling point?

Q 23.

Draw Newman and Sawhorse projections for the eclipsed and staggered conformations of ethane. Which of these conformations is more stable and why? .

Q 24.

(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

Q 25.

Explain the term aromaticity. What are the necessary conditions for any compound to show aromaticity?

Q 26.

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 mol1 and 296.8 kJ mol-1 What will be the other of reactivity of these halogen acids?

Q 27.

What will be the product obtained as a result of the following reaction and why?

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Q 28.

Despite their -I effect, halogens are o- andp-direction in haloarenes. Explain.

Q 29.

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’.

Q 30.

What do you mean by pyrolysis?

Q 31.

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Q 32.

What happens when benzene is treated with excess of Cl2 in presence of sunlight? Give chemical reaction.

Q 33.

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
 

Q 34.

Write structures of all the alkenes which on hydrogeneration give 2-methylbutane.

Q 35.

Classify the following compounds into (i) alkanes (ii) alkenes (iii) alkynes (iv) arenes.  (a) C6H6 (b) C4H8 (C) C8H8 (d) C5H8 (e) C6H14

Q 36.

(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.

Q 37.

What effect does branching of an alkane chain has on its boiling point?

Q 38.

What is electrophile in sulphonation?

Q 39.

How will you convert ethanoic acid into ethene?

Q 40.

Out of benzene, m-dinitrobenzene and toluene which will undergo nitration most easily and why?

Q 41.

What happens when benzene is treated with acetyl chloride in presence of AlCl3?

Q 42.

Explain the following with examples:
(i) Wurtz reaction
(ii) Hydrogenation.

Q 43.

For an electrophilic substitution reaction, the presence of a halogen atom in the benzene ring ;
(a) deactivates the ring by inductive effect
(b) deactivates the ring by resonance
(c) increases the charge density at ortho and para-positions relative to meta-position by resonance
(d) directs the incoming electrophile to meta-position by increasing the
charge density relative to ortho and para-positions. ‘

Q 44.

Draw the cis- and trans-structures for hex-2-ene. Which iosmer will have higher b.p. and why?

Q 45.

Why is benzene extra-ordinarily stable though it contains three double bonds?

Q 46.

Arrange the following carbanions in order of their decreasing stability.
(A) H3C-C ≡ C                                                                                
(B) H-C ≡ C
(C) H3C – CH2
(a) A>B>C
(b) B>A>C
(c) C>B>A
(d) C>A>B

Q 47.

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

Q 48.

Write the structure and IUPAC names of different structural isomers of alkenes corresponding to C5H10.

Q 49.

Why does the presence of a nitro group-make the benzene ring less reactive in comparison to the unsubstituted benzene ring? Explain.

Q 50.

What is Huckel rule?