Aromaticity

An aromatic compound follows Huckels rule (4n+2) and is planar. Although 1,5-trans[10]annulene agrees with Huckels Rule it is not planar; consequently it is not aromatic.

Rap

i can't picture this molecule in anything other than a planar conformation...can you explain how a non-planar conformation would occur?

The way I looked at it, the 1,5 trans bonds are somewhere in resonance between an sp3 and an sp2 electron configuration. Since an sp2 configuration found in cyclic aromatics is planar and all other bonds in 1,5-trans[10](trans) annulene are sp2 the majority of the compound is aromatically planar, but the sp3 bonds are not planar, the 1,5 trans bonds are strained in and out of the plane of the molecule and disturb the planar nature of this material. Moreover; the sp2/sp3 resonance of these two bonds make it available for reaction. Consequently, it is reactively unstable, nonplanar and non aromatic.

However, in my defense I am not an Organic Chemist--just a Chemical Engineer with some training and experience in Organic Chemistry.

Rap