Asked on 7^th December

Question : Which shape of SF₄ is more stable : I or II?

I

II

Answer : The structure (I) is more stable because repulsion is least when the lone pairs are at equatorial position.
Reference : Shapes of molecules are discuessed in Hybridisation.

Asked on 5^th November

Practice Questions Series [#7 Carboxylic Acids] :
We shared a link that contains some important questions (and answers) on "carboxylic acids". You can study them here : Practice Questions on Carboxylic Acids.

Asked on 22^nd October

Practice Questions Series [#6 Aldehydes and Ketones] :
We shared a link that contains some important questions (and answers) on "aldehydes and ketones". You can study them here : Practice Questions on Aldehydes and Ketones.

Asked on 16^th October

Practice Questions Series [#5 Ethers] :
We shared a link that contains some important questions (and answers) on ethers. You can study them in Practice Questions on Ethers.

Asked on 9^th October

Practice Questions Series [#4 Alcohols and Phenols] :
We shared a link that contains 15 important questions (and answers) on alcohols and phenols. You can study them in Practice Questions on Alcohols and Phenols.

Asked on 30^th September

Practice Questions Series [#3 Haloalkanes & Haloarenes] :
We shared a link that contains 15 important questions (and answers) on haloalkanes and haloarenes. You can study them in Practice Questions on Haloalkanes and Haloarenes.

Asked on 19^th September

Practice Questions Series [#2 Hydrocarbons] :
We shared a link that contains 15 important questions (and answers) from hydrocarbons. You can study them in Practice Questions on Hydrocarbons.

Asked on 3^rd September

Practice Questions Series [#1 Fundamentals] :
We shared a link that contains 15 important questions (and answers) on fundamentals of organic chemistry. You can study them in Practice Questions on Fundamentals of Organic Chemistry.

Asked on 20^th August

Question : Identify ?a, ?b and ?c.

Answer : Study the following points :

1. Alkyl halides undergo β-elimination with alcoholic KOH; therefore, ?a must be propene.
2. Alkenes react with HBr in the presence of peroxides to give haloalkanes according to anti-markovnikov's rule; therefore, ?b must be bromopropane.
3. Alkyl halides react with Na in the presence of dry ether to give alkanes with twice the number of carbon atoms present in the alkyl halide; therefore, ?c must be hexane. This reaction is known as Wurtz reaction.

Hence, the complete reaction is :

Reference : Reaction of alkyl halides with alc. KOH is discussed in preparation of alkenes. Reaction of alkenes with HBr and anti-markovnikov's rule are discussed in reactions of alkenes. Wurtz reaction is discussed in preparation of alkanes.

Asked on 13^th August

Question : Which one does not show cis-trans isomerism : CHCl═CCl₂, CHCl═CHCl, CH₃CH═CHCH₃?

Answer : CHCl═CCl₂ has identical atoms on the same side of double bond; therefore, it cannot show cis-trans isomerism.

Reference : Geometrical isomerism or cis-trans isomerism is explained in alkene.

Asked on 3^rd August

Question : Which carbocation is the most stable and which one is the least?

Answer : Due to hyperconjugation and inductive effect, the stability of carbocations follows the order :

Reference : Inductive effect and hyperconjugation are discussed in inductive and electromeric effect; and hyperconjugation respectively.

Asked on 24^th July

Question : What is the IUPAC name of this compound?

Answer : When a chain terminating functional group such as COOH, CHO appears more than two times in the parent chain, then their carbons are not included while numbering the parent chain. Hence, the IUPAC name of the above compound is :

Notice that the suffix 'carboxylic acid' is used in this case and not 'oic acid'. This compound is also known as citric acid.

Reference : Such compounds are discussed in Nomenclature of Polyfunctional Compounds.

Asked on 10^th July

Question : Find the hybridisation of each carbon.

Answer : Hybridisation of carbon depends on the number of atoms attached to carbon :

Hence, the answer is :

Reference : Hybridisation is discussed in Hybridisation.

Asked on 1^st July

Question : In the following compound, there is a hydrogen bond between nitrogen and hydrogen atoms (represented by dotted lines). Do you know if the bond is intermolecular hydrogen bond or intramolecular bond.

Answer : In intermolecular hydrogen bond, the hydrogen bond is formed between atoms of two different molecules. Example : Hydrogen bond between two different H₂O molecules. In intramolecular hydrogen bond, the hydrogen bond is formed between atoms of the same molecules.

Hence, the hydrogen bond in the asked compound is intramolecular hydrogen bond.

Reference : Hydrogen bond is discussed in Hydrogen Bonding.

Asked on 25^th June

Question : Do you know the IUPAC name of the following compound :

Answer : If a compound contains a functional group then the principal chain must contain it; therefore, the principal chain in the above compound contains six carbon atoms (and not eight).

Hence, the IUPAC name of the above compound is 2-propylhexanal.

Reference : Nomenclature of such compounds is discussed in Nomenclature of Compounds Containing One Functional Group. If you want to learn nomenclature from the very beginning, you should start from Nomenclature Introduction.