This set of Class 11 Chemistry Chapter 12 Multiple Choice Questions & Answers (MCQs) focuses on “Structural Representations of Organic Compounds”.
1. Identify the condensed formula of ethane from the following.
Explanation: In condensed formula, all the atoms are represented but single bonds are not shown. Only double and triple bonds will be represented. CH2=CH2 is not ethane; it is ethene.
2. Which is not a heteroatom?
Explanation: A heteroatom is any atom other than carbon or hydrogen atom. All the others apart from carbon mentioned above are heteroatoms. In other words, a heteroatom is a non-carbon atom present in a carbon structure.
3. No atoms are shown while representing structures in bond-line formula.
Explanation: Only carbon and hydrogen atoms are not shown in bond-line representation. But other atoms like oxygen, nitrogen, chlorine, etc. are shown. Bond-line representation of molecules is a skeletal representation in which the bonds are shown as single lines according to the bond order, i.e. one line for a single bond, two lines for a double bond and so on.
4. Identify the condensed formula of the given compound from the following.
a) Cl (CH2)2 (CH2)2CH (CH2)2CH2CH2CH3
b) Cl (CH2)3CH2CHCH2CH2CH2CH (CH3) 2
c) Cl (CH2)4CH (CH2)3CH (CH2) CH3
d) Cl (CH2)3CH2CH2CH (CH3)2CH3CHCH2CH3
Explanation: For determining the condensed formula, combine all the CH2 terms together and assign the appropriate number to them, each time checking that carbon only forms four bonds with the other atoms. Here, in the first part, i.e. ClCH2CH2CH2CH2CHCH2CH2CH2CHCH2CH3, there are four CH2 terms; so we group all these terms and represent them as (CH2)4. Similarly, combine the CH2 terms in the other parts and eventually we get the condensed formula of the above mentioned molecule.
5. Determine the bond-line formula of CH3CH2COCH2CH3.
Explanation: In CH3CH2COCH2CH3, the ketone group(C=O) is attached to the third carbon and therefore the double bond should be represented at the end of the second line, i.e. at the position of the third carbon. In all the other options, the ketone group is not attached to the third carbon, thereby, making them incorrect.
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