I need help understanding dipole momentin aromatic ring system?

Aromatic compounds are ring coumpounds having alternate single and double bonds and also satisfy huckle's rule i.e. It should contain 4n+2 no. of pi electrons. For example BENZENE, it is a six-membered ring with alternate double and single bonds. So it consists of six sigma bonds and three pi bonds. these pi bonds are made up of two pi electrons so the total no of pi bonds are three and hence the pi electrons are six. So 4*1+2=6.

Where n = no of rings. In benzene n=1

Now consider Napthalene n=2, So 4*2+2=10 no. of pi electrons should be there to become aromatic or ten pi electrons should be there. It consists of two hexagonal rings joined together with a single side sharing.

Similarly, Anthracene, Three hexagons joined by sharing two sides. No. of pi bonds are 7 and pi electrons are 14.

4*3+2=14

About dipole moment: these molecoles have ring currents due to which they do develope dipole moment depending on their structures or substituents.

aromatic ring system is a ring with which the electron is delocalized all around the ring, i.e. they have resonance structure and are resonance stabilized, as such it is relatively stable....

dipole moment in aromatic ring is dependent on the substituent on the ortho-, meta-, or para- positions whether they electron withdrawing group (EWG) or electron releasing group (ERG)

EWG stabilized the aromatic ring and the dipole moment is going to the substituent

ERG destabilized the aromatic ring and the dipole moment is going to the aromatic ring

aromatic ring structures are flat and have a ring current going. there is a dipole because of the ring current, but don't be lazy and read your organic text. if you don't understand it go talk to your professor or TA

Aromatic ring systems

http://en.wikipedia.org/wiki/Simple_aromatic_ring

Dipole moments

http://hyperphysics.phy-astr.gsu.edu/hbase/electri...