So because the oxygen is more electronegative than the carbon this carbon will develop a partial positive charge. This oxygen will develop a partial negative charge. By the same reasoning this will develop a partial negative charge and this also develops a partial negative charge. This has a partial positive charge, this has a partial positive charge and this nitrogen will have a partial negative charge. So we have a partial positive charge here and right next to it on the other molecule we have a partial negative charge on the nitrogen. And so we have the existence of these two partial charges that are opposite in nature and that will be an attractive force.