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318-20 - CH 318 N LECTURE 20 Textbook Assignment Chapter...

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CH 318 N LECTURE 20 Textbook Assignment: Chapter 21 (Begin) Homework (for credit): POW 10 posted Today’s Topics: Conjugated Systems; Benzene and Aromaticity Notice & Announcements: Exam Papers: pick up @ Chem Office Organic Lecture Series 2 Conjugated Conjugated Systems Systems (Omit 20.3) (Omit 20.3)
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Organic Lecture Series 3 from heats of hydrogenation-relative stabilities of conjugated vs unconjugated dienes can be studied: Δ H 0 -237 (-56.5) 1,3-Butadiene -126 (-30.1) -127 (-30.3) kJ (kcal)/mol Name 1-Pentene 1-Butene trans- 1,3-Pentadiene 1,4-Pentadiene trans- 2-Butene -115 (-27.6) cis- 2-Butene -120 (-28.6) -226 (-54.1) -254 (-60.8) Structural Formula Conjugated Conjugated Dienes Dienes conjugated Organic Lecture Series 4 conjugation of the double bonds in 1,3-butadiene gives an extra stability of approximately 17 kJ (4.1 kcal)/mol 2H 2 + catalyst Δ H 0 = 2(-127 kJ/mol) = -254 kJ/mol) 2 2 2H 2 + Δ H 0 = -237 kJ/mol catalyst Conjugated Conjugated Dienes Dienes
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Organic Lecture Series 5 Conjugated Conjugated Dienes Dienes C C C C H 2 C H C H C CH 2 The π systems of the 2 olefins overlap S-cis conformer Organic Lecture Series 6 C C C C H 2 C H C C H CH 2 S-Trans conformer Conjugated Conjugated Dienes Dienes
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