Date Part 3: Narrative Passage (20 pt Directions: The next questions are based o

Question

Date Part 3: Narrative Passage (20 pt Directions: The next questions are based on the passage below. Answer them to the best of your ability Effect of Aromaticity on Molecular Properties Aromaticity is a higher level of electron delocalization that dramatically alters the physical and chemical properties of species possessing this characteristic. Some of those properties are stability, polarity, acidity and chemical reactivity For a compound to be aromatic, it must be cyclic and possess adequate number of electrons and bonds. Each of the atoms that form the loop must provide an unhybudized p-atomic orbital. The p atomic orbitals are necessary for electron and charge delocalization in the ring which is the origin of stability in such molecular systems. For effective delocalization however, the ring atoms must collectively adopt a planar geometry. Planarity offers the highest overlap between the p-atomic orbitals This overlap provides a highway for electrons and/or charges to shuttle back and forth between and within the limits ofthe TT-system A T-framework in which there is delocalization is basically more stable than one with localizedelectrons and/or charges. When Ju-systems with similar number of atoms Ju-electrons and Ju-bonds are compared, the cyclic analog is usually more stable than the open chain analog. For example, 1,3,5-hexatriene and benzene have the same number of carbons, Ju-electrons and T-bonds. But the cyclic benzene is much more stable than the open chain hexatrjene. The closed loop of Ju-electrons creates a continuous or endless delocalization and it appears that this structural difference is the origin of the stark differences in the properties of cyclic and open chain delocalized systems. The following two examples illustrate how aromaticity dramatically alters the properties of otherwise comparable species Reactions in which aromatic species are products or intermediates are often possible and faster whereas such reactions are otherwise either impossible or very slow For example, hydrocarbons bearing sp -C-H bond are usually much weaker acids than compounds bearing hydrogen bonded to highly electronegative elements such as O halogens and S. But hydrocarbons such as cyclopentadiene (Scheme 1) are as strong acids as the alcohols and much stronger acids than carbonyl compounds with o-H This is because the conjugate base of the hydrocarbon is an aromatic anion

Explanation / Answer

14 a. answer is option (d) a Radical. the radical are only one electron which will not follow Huckels rule of aromaticity.

14 b. answer option (b) The structure must be planna. the one of the Huckels rule all atoms are involved in delocalization and the structure should be stable and helpful for delocaization.

14.c answer option (a) the reaction in which aromaticity destroyed or lost. The aromatic compounds are lower in energy and most stable form so destroy of aromaticity is increases the energy of the molecule so for that reaction very slow.

14. d. Answer option (c) The five membered ring of cyclopentadien is in the form anion it will be aromati but in the above case it is shows mutually share electron even in the Br atom more electronegative. THe  cyclopentadien also want negative charge for aromatic behavier so it is non- ionic.

14. e. Answer option (c). the three membered ring when it have the positive charge it wiil become a aromatic but herein it is negative charge so anti aromatic for that it is least stable.

Related Questions

Navigate

• Browse (All)
• Browse D
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.