[IrishAilish]

Indicate which of the metallation reactions given below would be thermodynamically favourable on the basis of the pKa data in non-aqueous media provided.


What is the underlying principle that determines whether the reaction occurs?
(a) C6H5Li + C6H5CH3 → C6H5CH2Li + C6H6
(b) LiCH2CH=CH2 + C6H5CH3 → C6H5CH2Li + CH3CH=CH2
(c) CH3Li + HC≡CH → HC≡CLi + CH4
(d) LiH + CH3CH=CH2 → LiCH2CH=CH2 + H2
(e) LiCH3 + CH3CH=CH2 → LiCH2CH=CH2 + CH4

Table pka values
HC≡CH 24
C6H6 37
CH4 48
C6H5CH3 35
H2 35
CH3CH=CH2 43


I don't understand anything in this question.. Can someone please give me a little help?

[gritch]

For these reaction I would suggest treating them as acid-base reactions and start by identifying your acid-base pair along with your conjugate acid-base pair. Thermodynamically the side that has the weaker acid-base should be favored.

For several of these you'll also need to remember what state the products are (i.e. H₂ would be a gas) and what that will do to the reaction equilibrium.

[orgo814]

evaluate which is hard and which is soft