Enthalpy of protodelithiation

The derived enthalpies of formation of the n-propyl and ec-butyl lithiated methoxy ethers are —260 and —275 kJmon, respectively, from equation 16, the enthalpies of protodelithiation, the enthalpy of formation of n-butyl lithium from Table 1 and of liquid n-butane, and the measured enthalpies of formation of methyl n-propyl ether (Iq, —266.0 ... 

Beak and Siegel studied the protodelithiation of the lithioanisole isomers by ethanol in di-n-butyl ether solution. As are phenyl lithium in diethyl ether solution and o-lithioanisole in dibutyl ether solution, the p- and m-lithioanisoles also were presumed to be predominately dimeric in the di-n-butyl ether solution. As dimers, the o-isomer is some 35 kJ mop more stable than the nearly isoenergetic m- and p-isomers, consistent with intramolecular association between the lithium and oxygen. That the inductive effect is small in comparison with association is shown by the nearly identical enthalpies of protodelithiation of the p- and m-lithioanisoles. 

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