Keynotes in Organic Chemistry oroundhis hiing eec vacant p-orbital 1.6.3 Mesomeric effects bond fra e elec e diffe Positive mesomeric effect eclcrons.thehaspoe ·>c=cH-8R onco nonin he Ci c8R 甲 Negative mesomeric effect cecons the hasaeaive aI-FaR C=CH-IR