MCQ
In the reaction sequence
- A
- ✓
- C
- D
✓
Answer
Correct option: B.
b
$(b)$ Copper $(I)$ salts have a remarkable effect on organometallic reagents. Grignard reagents add directly to the carbonyl group of $\alpha , \beta$ -unsaturated aldehydes and ketones to give allylic alcohols : you have seen several examples of this, and you can now explain it by saying that the hard Grignard reagent prefers to attack the harder $C = O$ rather than the softer $C = C$ electrophilic centre. Here is a further example - the addition of $MeMgBr$ to a cyclic ketone to give an allylic alcohol, plus, as it happens, some of a diene that arises from this alcohol by loss of water (dehydration). Below this example is the same reaction to which a very small amount (just $0.01$ equivalents, that is $1\%$) of copper $(I)$ chloride has been added. The effect of the copper is dramatic : it makes the Grignard reagent undergo conjugate addition, with only a trace of the diene.
$(b)$ Copper $(I)$ salts have a remarkable effect on organometallic reagents. Grignard reagents add directly to the carbonyl group of $\alpha , \beta$ -unsaturated aldehydes and ketones to give allylic alcohols : you have seen several examples of this, and you can now explain it by saying that the hard Grignard reagent prefers to attack the harder $C = O$ rather than the softer $C = C$ electrophilic centre. Here is a further example - the addition of $MeMgBr$ to a cyclic ketone to give an allylic alcohol, plus, as it happens, some of a diene that arises from this alcohol by loss of water (dehydration). Below this example is the same reaction to which a very small amount (just $0.01$ equivalents, that is $1\%$) of copper $(I)$ chloride has been added. The effect of the copper is dramatic : it makes the Grignard reagent undergo conjugate addition, with only a trace of the diene.
Organocopper reagents undergo conjugate addition:
The copper works by transmetallating the Grignard reagent to give an organocopper reagent. Organocoppers are softer than Grignard reagents, and add in a conjugate fashion to the softer $C = C$ double bond. Once the organocopper had added, the copper salt is available to transmetallate some more Grignard, and only a catalytic amount is required.
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
Explore more
Similar questions
The standard potential of a $Co^{+2}\,|\, Co$ electrode is $-0.28\, V$ and the standard potential of the cell $Pt\,|\,T{i^{2 + }}\left( {aq.} \right),\,T{i^{3 + }}\left( {aq.} \right)\,||\,C{o^{2 + }}\left( {aq.} \right)\,|\,Co\left( s \right)$ is $0.09\,V$. what is the standard potential of the $Ti_{\left( {aq.} \right)}^{2 + }\,|Ti_{\left( {aq.} \right)}^{3 + }$ electrode ........... $\mathrm{V}$
→Bakelite is obtained from phenol by reacting with:
$[Figure]$ $\mathop {\xrightarrow{{NaN{O_2}}}}\limits_{HCl} $ $A$ $A$ is
→Clemenson’s reduction of ketones is carried out in
Final product of following reaction contain
→$\begin{array}{*{20}{c}}
{C{H_3} - C \equiv C - C{H_2} - \mathop C\limits_{\mathop {||}\limits_O } - Cl}
\end{array} \ \xrightarrow[{BaS{O_4}}]{{{H_2} - Pd}}$
Identify a 'Chemical twin' among the followings.
Which of the following has highest electrode potential
Transition metals show paramagnetism
An alkaline gas, which produces dense white fumes when reacted with $\text{HCl}$ gas is $........$
→The substance that forms the plant cell walls is or Which carbohydrates is an essential constituents of plant cells