Haloalkanes and Haloarenes quiz

The best reagent for converting an alcohol into an alkyl chloride is:

The Swarts reaction is used to prepare:

SN2 reactions proceed with:

Which is most reactive towards SN1?

Addition of HBr to propene in the presence of peroxide gives:

Chlorobenzene on heating with NaOH at 623 K and 300 atm, followed by acidification, gives:

The reaction of an aryl halide with an alkyl halide and sodium in dry ether is called:

Chloroform on exposure to air and light forms the poisonous gas:

Which is optically active?

Halogens in haloarenes are:

Why are haloalkanes insoluble in water although they are polar? (2 marks)

Why is the boiling point of 2-bromo-2-methylpropane lower than that of 1-bromobutane? (2 marks)

Why are Grignard reagents prepared under anhydrous conditions? (2 marks)

Why does p-dichlorobenzene have a higher melting point than its ortho and meta isomers? (2 marks)

What is meant by chirality? Give one example of a chiral molecule. (2 marks)

Why is allyl chloride more reactive than n-propyl chloride towards SN1 reactions? (2 marks)

Write the equation for the preparation of chlorobenzene from benzenediazonium chloride by the Sandmeyer reaction. (2 marks)

KCN gives alkyl cyanides while AgCN gives isocyanides with haloalkanes. Explain. (2 marks)

Write the equation for the Fittig reaction. (2 marks)

State two uses and two harmful effects of carbon tetrachloride. (2 marks)

0.25 g of an organic compound gave 0.287 g of AgCl in the Carius method. Calculate the percentage of chlorine (AgCl = 143.5, Cl = 35.5). (3 marks)

Calculate the mass of ethanol formed when 6.45 g of chloroethane (C2H5Cl = 64.5) reacts completely with aqueous KOH (C2H5OH = 46). (3 marks)

An SN2 reaction has rate = k[RX][Nu-]. If both concentrations are tripled, by what factor does the rate increase? For an SN1 reaction with rate = k[RX], what is the factor? (3 marks)

Calculate the volume of methane at STP obtained when 14.2 g of iodomethane (CH3I = 142) is converted to a Grignard reagent and then treated with water (molar volume 22.4 L). (3 marks)

A compound C3H7Br on treatment with alcoholic KOH gives propene. Calculate the mass of propene (C3H6 = 42) formed from 24.6 g of C3H7Br (123), assuming 75% yield. (3 marks)

Read the passage and answer the questions. A chemist treated optically active (+)-2-bromobutane with aqueous NaOH in a polar protic solvent and obtained a product with almost zero optical rotation. In another experiment, with a strong nucleophile in an aprotic solvent, the product had the opposite configuration. (i) Name the mechanism in each case. (ii) Explain the loss of optical activity in the first case. (iii) Why did the configuration invert in the second case? (5 marks)

Read the passage and answer the questions. When propene reacts with HBr, the major product is 2-bromopropane. In the presence of benzoyl peroxide, however, 1-bromopropane is the major product. (i) Name the rules or effects involved. (ii) Write the equations. (iii) Why does HCl not show this effect? (5 marks)

Read the passage and answer the questions. DDT was the first chlorinated organic insecticide and was used widely to control mosquitoes. Later, many insects became resistant and the chemical was found to accumulate in fish and birds. (i) Give the full chemical name of DDT. (ii) Why does it accumulate in the food chain? (iii) Why was it banned in many countries? (5 marks)

Read the passage and answer the questions. Chlorobenzene does not react with aqueous NaOH under normal conditions, but 2,4,6-trinitrochlorobenzene reacts with warm water to give picric acid. (i) Why is chlorobenzene unreactive? (ii) How do the nitro groups increase reactivity? (iii) Write the equation for the reaction with warm water. (5 marks)

Read the passage and answer the questions. Freons such as CCl2F2 were used in refrigerators and aerosol sprays because they are non-toxic, non-corrosive and stable. However, they diffuse into the stratosphere. (i) How do freons damage the ozone layer? (ii) Why are they called stable? (iii) Name one alternative used now. (5 marks)

Describe four methods of preparation of haloalkanes with equations, including halogen exchange reactions. (6 marks)

Explain the SN1 and SN2 mechanisms with diagrams, and compare them on five bases. (6 marks)

Explain optical isomerism with reference to 2-bromobutane. Draw the enantiomers and explain retention, inversion and racemisation. (6 marks)

Explain the reactions of haloarenes: nucleophilic substitution, electrophilic substitution (halogenation, nitration, sulphonation, Friedel-Crafts) and reaction with metals, with equations. (6 marks)

Describe the uses and environmental effects of dichloromethane, chloroform, iodoform, carbon tetrachloride, freons and DDT. Draw a chart summarising them. (6 marks)