This set of Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Haloalkanes Nomenclature”.
1. What is the common name of 3-Bromopropene?
a) Tert-Butyl bromide
b) Vinyl bromide
c) Allyl bromide
d) Propylidene bromide
Explanation: 3-Bromopropene has 3 C atoms in the parent chain with a double bond at C-1 and Br at C-3. This means that Br is attached to the C which is next to the C-C double bond, hence it is an allylic halide.
Explanation: The longest chain of C atoms is 4 (butene) and the numbering should begin from the Br side to satisfy the lowest set of locants rule. So, Br is at C-1 and double bond is at C-2.
Explanation: All the names given are appropriate for the shown compound, but m-Chlorotoluene is the common name and not the IUPAC name.
4. In the common naming system, the prefix sym- is used for haloarenes with _____ halogen atoms.
Explanation: The prefix sym- is used for trihaloarenes with same halogen atom at alternate positions in the benzene ring (1, 3, 5). The prefixes o-, m- and p- are used for dihaloarenes depending on the relative positions of the two identical halogen atoms on the aromatic ring.
5. How many carbon atoms does Isobutyl chloride have in its parent carbon chain?
Explanation: The IUPAC name of Isobutyl chloride is 1-Chloro-2-methylpropane, which means the parent chain consists of 3 carbon atoms with an alkyl group at C-2 and a halogen at C-1.
6. Identify the correct naming of the compound H3C-CHCl2 from the following?
a) Ethylidene chloride
b) Ethylene dichloride
Explanation: The given compound is a dihaloalkane with both the halogens on the same carbon atom. These are also known as gem-dihalides or alkylidene halides.
7. Identify the correct common name for CH3CH2CH2CH2Cl.
a) Isobutyl chloride
b) n-Butyl chloride
c) sec-Butyl chloride
d) tert-Butyl chloride
Explanation: The compound shown is 1-Chlorobutane which has 4 C atoms in the parent chain and the only halogen compound present at the end of the chain. This type structure has the prefix n- in the common name.
8. What is the IUPAC name for the compound (CH3)3CCH2Cl?
Explanation: There are two different possible chains that consists of maximum 3 C atoms. One of them has two methyl and one chloro group and the other has one methyl and one complex substituent. The preference is given to the former with the chloro at C-1 and the 2 methyl groups at C-2.
9. What is the IUPAC name of the compound shown?
Explanation: The alkyl group is alicyclic with 4 carbon atoms at the corners of a rectangle and a double bond; hence the base is cyclobutene. In the case of cyclic alkenes, the position of double bond is always given the first number.
10. What is the correct IUPAC naming of CHF2CBrClF?
Explanation: There are only two C atoms in the compounds and only single bonds with two F atoms at C-2 and one of each F, Cl and Br at C-1.
11. The compound 2,2-Dichlorobutane is a geminal dihalide.
Explanation: The compound is dihaloalkane with 2 chlorine atoms one the same carbon atom, hence it is a gem dihalide.
Explanation: The parent carbon chain must include the double bond, so there are 4 C atoms including the C-C double bond and the double bond is present at C-1 with two methyl groups at positions 2 and 3.
13. The correct naming of the compound CH≡C-CH=CH-CH3 is __________
Explanation: The lower set of locants is 1, 3 rather than 2, 4. This compound is named as a derivative of alkyne and not alkenes. Also, the terminal ‘e’ in ene is dropped because it comes before ‘y’ of yne.
14. The prefix bis is used when two complex substituents are present on the same of different C atoms on a hydrocarbon.
Explanation: The prefix bis is used instead of di for complex substituents in hydrocarbons before the name of the substituent which is enclosed in brackets.
15. How many isomers does C5H11Br have?
Explanation: It has a total of 8 isomers, four are primary and two each are secondary and tertiary haloalkanes.
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