The most suitable reagent for the conversion of
(JEE Main 2014)
Mild oxidising agents like PCC (Pyridinium chlorochromate) are particularly used for the conversion of
An unknown alcohol is treated with the ‘Lucas reagent' to determine whether the alcohol is primary, secondary or tertiary. Which alcohol reacts fastest and by what mechanism?
(JEE Main 2013)
The reaction of alcohol with Lucas reagent is mostly SN1 reaction and the rate of reaction is directly proportional to the stability of carbocation formed in the reaction.
Since, 3° R—OH forms 3° carbocation (most stable) hence, it will react fastest by SN1 reaction.
Consider the follow ing reaction,
Among the following, which one cannot be formed as a product under any conditions?
Options (a), (b) and (d) may be formed but option (c) is never formed.
From amongst the following alcohols the one that would react fastest with conc. HCI and anhydrous ZnCI2 is
The reaction of alcohol with cone. HCI and anhydrous ZnCI2 follows SN1 pathway, so greater the stability of carbocation formed, faster is the reaction,2-methylpropan-2-ol gives 3° carbocation. Hence, it reacts rapidly with cone. HCI and anhydrous ZnCI2 (Lucas reagent).
The main product of the following reaction is
In the following sequence of reactions,
the compound D is
Among the following the one that gives positive iodoform test upon reaction with I2 and NaOH is
For positive iodoform test, alcohol molecule must have
Thus, iodoform test is given by only (d) while others will not give this test.
Acid catalysed hydration of alkenes except ethene leads to the formation of
Hydration of ethene gives 1° alcohol (ethanol) while all other alkenes give either 2° or 3° alcohols.
Among the following compounds which can be dehydrated very easily?
Dehydration of alcohol is in the order 1°< 2° < 3°
Thus (c), a 3° alcohol is dehydrated very easily.
An ether is more volatile than an alcohol having the same molecular formula. This is due to
Alcohol has polar H which makes intermolecular H-bondin g possible. Ether is non-polar, hence has no H-bonding. Lack of H-bonding in ether makes it more volatile than alcohol.
During dehydration of alcohols to alkenes by heating with concentrated H2SO4 the initiation step is
Protonation of —OH is first step. It involves conversion of poor leaving group (—OH) into good leaving group
Maximum dehydration takes place in that of
Dehydration takes place with the formation of more stable carbocation. Among the given compounds, only compound (b) forms conjugated carbocation. Thus, maximum amount of dehydration takes place in compound (b).