In chemistry, a conjugated system is a system of connected p-orbitals with delocalized electrons in molecules with alternating single and multiple bonds, which in general may lower the overall energy of the molecule and increase stability. Lone pairs, radicals or carbenium ions may be part of the system. The compound may be cyclic, acyclic, linear or mixed. Conjugation is the overlap of one p-orbital with another across an intervening sigma bond (in transition metals d-orbitals can be involved). A conjugated system has a region of overlapping p-orbitals, bridging the interjacent single bonds. They...

In organic chemistry, Hückel's rule estimates whether a planar ring molecule will have aromatic properties. The quantum mechanical basis for its formulation was first worked out by physical chemist Erich Hückel in 1931. The succinct expression as the 4n+2 rule has been attributed to von Doering (1951), although several authors were using this form at around the same time. A cyclic ring molecule follows Hückel's rule when the number of its π-electrons equals 4n+2 where n is zero or any positive integer, although clearcut examples are really only established for values of n = 0 up to about n = 6...

Nowruz (Persian: Nowruz – نوروز‎‎; [nouˈɾuːz]; literally "New Day") is the name of the Iranian New Year, also known as the Persian New Year, which is celebrated worldwide by Iranian peoples, along with some other ethno-linguistic groups, as the beginning of the New Year. It has been celebrated for over 3,000 years in the Balkans, the Black Sea Basin, the Caucasus, Central Asia, and Western Asia. It marks the first day of Farvardin in the Iranian calendar. Nowruz is the day of the astronomical vernal equinox, and marks the beginning of spring in the Northern Hemisphere. It usually occurs on March...