Through conjugation

The suggestion outlined above about the way in which through-conjugation influences the nitration of p-chloronitrobenzene is relevant to the observed reactivities (ortho > meta > para) of the isomeric chloronitrobenzenes. Application of the additivity principle to the... 

Nitroparaffins and HBF react with alkynes through conjugate addition of a proton and the nitronate ion at the triple bond as illustrated by nitromethane and 5-decyne (53). 

In a, P-unsaturated carbonyl compounds and related electron-deficient alkenes and alkynes, there exist two electrophilic sites and both are prone to be attacked by nucleophiles. However, the conjugated site is considerably softer compared with the unconjugated site, based on the Frontier Molecular Orbital analysis.27 Consequently, softer nucleophiles predominantly react with a, (i-unsaturated carbonyl compounds through conjugate addition (or Michael addition). Water is a hard solvent. This property of water has two significant implications for conjugate addition reactions (1) Such reactions can tolerate water since the nucleophiles and the electrophiles are softer whereas water is hard and (2) water will not compete with nucleophiles significantly in such... 

An exactly analogous situation will arise where there is the possibility of direct through-conjugation between a suitable electron-donating p-substituent and a reaction centre at which +ve charge is developing. A good example is solvolysis (SN1) of the... 

Solvolysis of the p-MeO and p-Me chlorides is found to be faster (p-MeO 800 times) than would have been predicted from their op. values. This stems from the stabilisation, by through-conjugation, of the carbocationic intermediates (21a and 21b) which are developing during the slow, rate-limiting step of the overall reaction ... 

There have been a number of attempts, by the introduction of a further parameter into the Hammett equation, to quantify this graded response—via through-conjugation—on the part of a p-substituent. Among the best known of these is the Yukawa-Tsuno equation, [7], which, in the form shown here, is... 

Solomon GC, Andrews DQ, Van Duyne RP, Ratner MA (2009) Electron transport through conjugated molecules when the 7t system only tells part of the story. ChemPhysChem 10(l) 257-264... 

Joachim C, Launay JP, Woitellier S (1990) Distance dependence of the effective coupling parameters through conjugated ligands of the polyene type. Chem Phys 147 131... 

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