CHEM 3410 1st Edition Lecture 5 Outline of Current I. Correction to ENDO/EXO II. Common names of Benzene Derivatives III. Benzene and Aromaticity (Continued)A. Rules of AromaticityB. Anti-Aromatics IntroductionC. Applying the rulesD. Aromaticity and AcidityE. HeterocyclesOutline of Last LectureI. Diels-Alder StereochemistryII. Diels-Alder Cyclic ReactionsA. Diels-Alder reactions beginning with a Cyclic DieneIII. Benzene and AromaticityA.Definition of AromaticityB.Physical CharacteristicsC.Substitution patterns ( Para, Meta, Ortho)IV.Common Names of Aromatic ringsCurrent LectureI. Correction to ENDO/EXOWhen he introduced this trend 1/21, he mixed up the terms ENDO and EXO. Everything he said about the chemistry was correct, he just mixed the vocabulary. Check D2L for his hand out.There is something more about the stereochemistry that you must note. The bridge is in the up position and the carbonyls are in the down positions. When discussing diels-alder cyclic products, you refer to this phenomenon as the “endo product” (down). You will only ever see endo products*! Recall hindrance! If the carbonyls were in the up position, they would be an “exo product” Bridge UP, Groups DOWN = Endo; Bridge DOWN, Groups UP = Exo These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.You can easily mess up a quiz or exam if you are not careful drawing the six membered, 2D ring. Practice drawing the 3D chairs instead to help yourself understand and to show Dr. Harden you really understand when he is grading your papers. *If you start with a trans-dienophile, you will get an exo product. You will just have to remember that the endo is more favorable.Of course, you will also put your groups in the down/ endo position on their respective carbons as well if necessary.II. Common names of Benzene Derivatives There are others that you must know that will be listed on your take home quiz (1/23), and those can be found in your book in Chapter 15.III. Benzene and Aromaticity A. Rules of Aromaticity (To be aromatic….)1. Must be cyclic2. Must be COMPLETELY conjugatedi. Every atom in that ring must be sp2 hybridized. It the uninterrupted overlap of p orbitals that leads to the complete conjugation.3. Must have 4(n)+1 pi electrons. (Huckle Numbers)i. n= whole number interger1. 4(0)+2=22. 4(1)+2=63. 4(2)+2=104. 4(3)+2=14ii. The Huckle numbers you need to go are 2,6,10, and 14. You will only go up to 14 pi electrons in Dr. Harden’s class. Just write that list on your tests and quizzes so you won’t forget.4. Must be planari. We can’t tell by just looking at the pictures….all cyclos look planar on paper. We assume that if the other 3 criteria are met, then the moleculeis planar. Remember that cyclohexane makes bridges and chairs, so that iswhy it is not aromatic. However, Benzene meets the above criteria and is planar.B. Anti-Aromatics1. Anti-aromatics meet criteria 1 and 2, but they do not meet 3. 2. Nonaromatics would not meet 1 or 2 (may not be cyclic and/or FULLY conjugated)3. Also, anti-aromatics are less stable than we would predict. Aromatics are more stable than we would predict. Non-aromatics are as stable as theory would predict4. Structural Issues:i. In anti-aromatics, the electrons are localized. They cannot overlap due to structural issues. Notice that in the structure below, you can see the chair for octatetraene (the first structure in “Applying the rules”). The p orbitals are titled in a way that the electrons cannot travel about the molecule in a delocalized fashion.1. Anti-aromatics will always have a structural disadvantage that does not allow p orbital overlap.a. This causes them to be much less stable!C. Applying the Rules:Cyclobutadiene (the structure above) is so unstable that it reacts with itself. Cyclobutadiene does a Diels-Alder reaction with itself because it is so ridiculously unstable. When purchasedcommercially, you buy the Diels-Alder product and have to thermally crack it. You have to freeze it in a 0 C ice bath and only have 22 minutes to use it before it reacts again.You will also see ions, and these molecules may also be aromatic if under they meet all of the rules. D. Aromaticity and Acidity: If the something generated is aromatic, it is more likely to happen. The reactionis more favorable. If the something generated is anti-aromatic or not aromatic, it is not favorable.Review of Anti-aromatic vs AromaticE. HeterocyclesHeteroatoms are nonmetals that are not carbon. Heterocycles are cyclics that contain at least one