A letter to grandma about aromaticity

205 Warren Place

Campbellsville, KY 42718

February 23, 2011

Mrs. Peggy Monson

112 Lane Way

Campbellsville, KY 42718

Dear Granny,

I’m going to explain the lay out of aromaticity, which is another word for fragrance. The structures of these compounds have double bonds regularly, but they don’t in fact behave like a double bond. Reagents such as bromine for example react with benzene by substitution instead of addition. Benzene and its derivatives are referred to as aromatic because of there unique odors. The aromaticity of the benzene ring can be assessed by measuring its resonance energy. A way to this is by measuring its heat of hydrogenation which is a Kekule formula. Both the heat of hydrogenation and combustion will have double bonds present, along with its bond distances being uniform, which is measured by spectroscopy. Also it will have longer wavelengths absorption bands in the ultraviolet region of the spectrum.

Huckel’s rule determines the number of π electrons that provide stability to an unsaturated planar ring. Huckel’s rule uses the formula 4n + 2. Although most polycyclic aromatic molecules follow Huckel’s rule some don’t, like pyrene, which has sixteen π electrons and is aromatic. For benzene, n = 1 and when put in the formula equals six (4n + 2 = 6), which is an aromatic sextet. The rule was calculated for single ring molecules and generally doesn’t apply to multiring systems. Also NMR can be used to measure the degree of aromaticity in a molecule by how well its ring of π electrons can maintain an induced ring current. In other words, it can be diatrophic which is were π electrons are delocalized and proteins are attached to the ring and it is shifted downfield in the nuclear magnetic resonance spectrum or NMR, where double bonds are present.

Overall, I hope I helped you understand the concept of aromaticity and I hope to see you soon.

Sincerely you’re favorite,

Alexia

Questions I was expecting to be on test!

For chapter 13 and 14 test, I expected a lot more questions from the sapling or even questions like the sapling. I studied the sapling a lot more then anything else because it basically had a question from each section in chapter 13 and 14. I know there were 5 questions, but I was expecting more then just 5 questions from the sapling. Also there were a lot of problems involving CNMR and HNMR spectrum and with that being, I was expecting there to be a problem like number 15 and 16 on the sapling, where it ask you to tell how many unique HMNR and CNMR signals exist for each compound, but instead there hardly wasn't anything about signals on the test. I also expected there to be a problem like number 17 on sapling, where it asked you to give the chemical shifts in parts per million (ppm) and it gave you the HMNR signal in Hz and the instrument in MHz. Overall, I thought the test was pretty hard and challenging and even though I was expecting a few more questions from sapling, I think I was hoping there would be to. I also think even though sapling gives you the answers and you can even hit solution to see the right answer, you still get to see how it’s done and you get a chance to look in your book for help, which you learn more by doing so.