Haloalkanes and Haloarenes

Class 12th Chemistry – 10 Haloalkanes and Haloarenes MCQs

Groups like cyanides and nitrites possess _________nucleophilic centre(s) and are called ‘ambident nucleophiles’.

Correct! Wrong!

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Cyanide group is a hybrid of two contributing structures [-C≡N ↔: C=N-] and therefore can act as a nucleophile in two different ways i.e. by linking through carbon atom it results in alkyl cyanides (RCN). And through nitrogen atom it leads to isocyanides (RNC).

When a compound rotates the plane polarized light to the ____ in ____ direction, the compound is called laevorotatory.

Correct! Wrong!

Laevorotatory refers to the rotation of the plane of vibration of polarized light to the left (as seen by an observer looking towards the incoming light).

Tetrachloromethane is also known as ____ .

Correct! Wrong!

Tetra chloro refers to having 4 chlorine atoms. Carbon tetrachloride also refers Knowledge to the same compound.

Given below are some of the uses of tetrachloromethane (Carbon tetrachloride, CCl4). Of these, the one that is false is ____

Correct! Wrong!

When carbon tetrachloride is released into the air, it rises to the atmosphere and depletes the ozone layer resulting in human exposure to ultraviolet rays leading to skin cancer, eye diseases and disorder and possible disruption of the immune system.

Grignard reagents are highly reactive and react with any source of ____ to give hydrocarbons.

Correct! Wrong!

Grignard reagents are highly reactive and react with any source of proton to give hydrocarbons. Even water, alcohols, amines are sufficiently acidic (acids are provider of proto i.e. H+) to convert them to corresponding hydrocarbons. RMgX + H2O → RH + Mg(OH)X. Option C is correct.

Nucleophilic reactions are the most useful classes of organic reactions of alkyl halides in which halogens are bonded to __________-hybridized carbon.

Correct! Wrong!

OH- + CH3Cl → CH3OH + Cl-.The equation given above is that of a nucleophilic substitution. As is clear from the equation above, the carbon atom is having 4 groups attached with a single bond, each which is said to be sp3 hybridized, as they are made of one 2s electron and three 2p electrons. Correct choice is B.

Of the options give, the one statement about trichloromethane (Chloroform) that is correct is ____

Correct! Wrong!

Option B is true. When exposed to sunlight, it forms the poisonous gas phosgene and hence, it should be stored in a dark place. When chloroform is reduced with zinc dust and water, methane is obtained. Chlorination of chloroform with chlorine in the presence of diffused sunlight gives carbon tetrachloride.

In Fittig reaction, aryl halides when treated with ____ in dry ether give an analogous compound in which two aryl groups are joined together.

Correct! Wrong!

Sodium is the only element used in Fittig reaction.

Alkyl halides are prepared from alcohols, which are easily accessible. The hydroxyl group of an alcohol is replaced by halogen on reactions with certain compounds. Of the options given, the compound that is incorrectly given is __.

Correct! Wrong!

Na always forms monohalides (NaX). Option B gives a wrong compound.

The length of C-Cl bond in haloalkane is. ____ pm while in haloarene, it is ____pm.

Correct! Wrong!

The length of C-Cl bond in haloalkane is 177 pm while in haloarene, it is 166 pm.

At room temperature ethyl chloride, methyl bromide, ethyl chloride and some chlorofluoromethanes exist as____.

Correct! Wrong!

In alkyl halides with lesser number of carbon atoms (1-4), the intermolecular van der Waals forces are weak so the molecules do not come closer. Therefore, they exist as gases at room temperature.

The replacement of hydrogen atom by the element/s _________ in an aliphatic or aromatic hydrocarbon results in the formation of haloalkane or haloarene respectively.

Correct! Wrong!

F, Cl, Br and I are known as halogens. Therefore, if a hydrogen atom(s) from an alkane or arene is (are) replaced by any of the halogen atom(s), the compound is known as haloalkane or haloarene respectively.

Aryl chlorides and bromides can be easily prepared by ____ of arenes with chlorine and bromine respectively in the presence of Lewis acid catalysts like iron or iron (III) chloride.

Correct! Wrong!

Electrophilic substituting into the ring gives a mixture of 2-chloromethylbenzene and 4-chloromethylbenzene. The ortho and para isomers can be easily separated due to large difference in their melting points. Option B is correct.

Of the following, ____________ is not a monohalo-organic compound.

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All compounds except C have one halogen, whereas C has two Cl-atoms (i.e. dihalo not monohalo). So, CH2Cl2 is not a monohalo-organic compound.

Given below are some properties of Freons12 gas. The statement that is incorrect is____

Correct! Wrong!

Freon is slightly soluble in water at a level of approximately 0.3 grams per liter at room temperature.

When a beam of plane polarized light is passed through certain solutions, the plane of polarization of the light that emerges is rotated relative to the original plane. This phenomenon is known as ____

Correct! Wrong!

When a beam of plane polarized light is passed through a solution of a chiral compound such as (S)-alanine, the plane of polarization of the light that emerges is rotated relative to the original plane. This phenomenon is known as optical activity, and compounds that rotate the plane of polarized light are said to be optically active.

Aryl halides are extremely less reactive towards nucleophile substitution reactions due to all but one of the following reasons. The incorrect reason is

Correct! Wrong!

Nucleophile and haloarenes are both electron-rich. Hence, there is repulsion instead of attraction between them. Halogen atom attached to arene is electron-rich and so is a nucleophile. Option D is wrong.

The chloroflurocarbon compounds of methane and ethane are collectively known as ____

Correct! Wrong!

Freon is DuPont's trade name for chlorofluorocarbon and hydrochlorofluorocarbons. In other countries, the same family of chemical compounds is called Isceon, Ledon, Frigen, Kaltron, Flugene, Forane, Fridohna, Frigedohn, etc.

In alkyl halides, due to greater polarity as well as higher molecular mass, as compared to the parent hydrocarbon, the intermolecular ___________ and ___________ of attraction are stronger in the halogen derivatives.

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In alkyl halides, due to greater polarity as well as higher molecular mass, as compared to the parent hydrocarbon, the intermolecular dipole-dipole and van der Waals forces of attraction are stronger in the halogen derivatives.

The metal present in Grignard reagents is___.

Correct! Wrong!

Grignard reagents use only magnesium. Option C is correct.

Haloalkanes react with KCN to form__________ as main product, but with AgCN, it form _______ as the chief product.

Correct! Wrong!

KCN has mainly ionic and provides cyanide ions in solution. Although, both carbon and nitrogen atoms are capable of providing electron pairs, the C-C bond that is formed (in RCN, alkyl cyanide) is more stable that C-N bond. Whereas, in AgCN (Ag-CN:) though all the bonds are covalent, but since nitrogen is free to donate an electron pair, this results in formation of isocyanide (RNC) as the main product.

Which of the following is not an Electrophilic substitution reaction of haloarenes?

Correct! Wrong!

Wurtz-Fittig reaction is not an electrophilic reaction. This reaction allows the alkylation of aryl halides. The more reactive alkyl halide forms sodium first, and this reacts as a nucleophile with an aryl halide as the electrophile.

Triodomethane (Iodoform) was earlier used as an…

Correct! Wrong!

Antiseptic properties are due to the liberation of free iodine and not due to iodoform itself. However, due to its objectionable smell Iodoform is not used now.

The spatial arrangement of four groups (valences) around a central carbon atom is tetrahedral and if all the substituents attached to that carbon are different, and then such a carbon is called ____

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Only atoms are symmetric or asymmetric. The spatial arrangement of four groups (valences) around a central carbon atom is tetrahedral and if all the substituents attached to that carbon are different, then such a carbon known to be assymetric. It is also known as stereo centre. Option C is correct.

In the preparation of alkyl halides, the one statement that is incorrect is ____ .

Correct! Wrong!

The correct order of reactivity is 30>20>10. Option B gives wrong information.

To produce Grignard reagents only alkyl____ are used with magnesium metal, in dry ether.

Correct! Wrong!

Only alkyl halides are used in the reaction, producing Grignard reagents. Option A is correct.

Alkyl halides react with sodium in dry ether to give hydrocarbons containing double the number of carbon atoms present in the halide. This reaction is known as ____ reaction.

Correct! Wrong!

This reaction is known as Wurtz reaction after the name of its originator. As it is clear from the equation given below, the product has twice the number of alkyl group than that present in the alkyl halide used. 2RX + 2Na → RR + 2NaX. Option C is correct.

The statement about Dicholoromethane (Methylene chloride) that is not correct is

Correct! Wrong!

Chloroform is used in the production of Freon refrigerant R-22 and not Methylene chloride.

Boiling points of the isomeric dihalobenzens are very nearly the same. However, the ____ -isomers are high melting as compared their other two isomers. It is due to symmetry of ____ isomers that fits in crystal lattice better as compared to other two isomers.

Correct! Wrong!

As is clear from the figure below, the para- isomer is symmetrical and so it fits in the crystal lattice better as compared to other two isomers. Hence, it is difficult to remove as compared to the other ill-fitting isomers. Thus, the boiling point of para- isomer is comparatively higher.

When we go down the group 17 in the periodic table, the one option that is incorrect is ____.

Correct! Wrong!

When we go down the group 17 in the periodic table, the reactivity decreases. Option D is wrong.

Class 12th Chemistry - 10 Haloalkanes and Haloarenes MCQs
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Class 12th Chemistry - 10 Haloalkanes and Haloarenes MCQs