1. Chemistry 125: Lecture 64 April 1, 2011 Triphenylmethyl Carbonyl Compounds: Overview This For copyright notice see final page of this file

2. Ph 3 C Propeller Conformation Ph H-H contact prevents bonding

3. Two Ph 3 C Propellers Hopelessly Remote

4. Steric hindrance in triphenylmethyl causes twists that reduce overlap with 2p C by 25% from diphenylmethyl. It also makes tetraphenylmethane very difficult to prepare, not to mention hexaphenylethane !

5. Friedel-Crafts or Ph 2 Mg Tetraphenylmethane (1897) “I have tried to solve this problem in a completely different way.” ? 8 g 110° Cu 0.3 g Solubility Analysis : C 93.32 (93.75) H 6.36 (6.25) 100 mg for Mol. Wt. : 0.289° 306 (320 calc.) (by solvent b.p. elevation)

6. O 2 N- - 3 C - + EtOH O 2 N- - 3 C-H EtO - Back in Ann Arbor (1898-9) Confirmed Mol. Wt. 0.285° 318 (320 calc.) “Unlike the trinitrotriphenylmethane… it does not dissolve in sodium ethylate, nor does it give any coloration…” How about O 2 N- - 3 C-C - -NO 2 3 ? Prepared O 2 N- - 4 C (99.5% yield)

7. Prepared "Hexaphenylethane" C+H = 93.97, 94.20, 94.00, 94.57% from first 4 methods. Reported more than 17 methods. Prepared authentic peroxide from Na 2 O 2 (S N 2). Prepared hydrocarbon in CO 2 atmosphere using special apparatus with ground glass joints. Ph 3 C - Cl Zn Ph 3 C - CPh 3 Ph 3 CO - OCPh 3 O2O2 ( C+H = 93.82% )

8. Free Radical! (1900) Highly “Unsaturated” (O 2, Cl 2, Br 2, even I 2 !) Launched an American Century of Chemistry

9. October, 1900

10. Paris (Wurtz - Médicine) Cornell MIT Paris ( Friedel - Mines) President AlCl 3 /C-Electrophile: The Friedel-Crafts Reaction 1877 Gibbs Equilibrium 1876-8

11. age Moses Gomberg Publications (1888-1942) Munich-Heidelberg Two Gomberg papers from this period contained more graphs than all 4290 pages of Berichte in 1900. Launching the American Chemical Century CPh 4 (1896) CPh 3 (1900)

12. Second Thoughts on Friedel-Crafts This

13. What if CH 3 gets stuck halfway? Rearrangement in Friedel-Crafts Alkylation AlCl 3 + Cl + AlCl 3 + H gives n-PrPh product gives i-PrPh product Cl AlCl 3 + CH 3 gives n-PrPh product Hydride Shift why not Methide Shift? Protonated Cyclopropane (stability between 1° and 2° cations) Still H + 3/72/7 Deno (1968) D+D+ Which of these gives the n-PrPh product in Friedel- Crafts? CH 3 + + Nu with one D Where? PROBLEM: How to decide? gives n-PrPh product! Still

14. Carbonyl Compounds This e.g. J&F Chapters 16-19 (268 pages!) Good News: Much of this is review!

15. Chapter 16: Aldehydes & Ketones C=O Stable, but Reactive! Average Bond Energies (kcal/mole) C-C 83 C=C 146 C-O 86 C=O 176 (aldehyde) 179 (ketone) “second bond” 63 90 93 (more substituted sp 2 C )

16. 100 MHz 13 CMR Spectrum Proton Decoupled (from Chem 220) HC O CH n 199.6 31.2 CH n 201.8 37.6 5.2 CH 3 201.6 45.7 15.713.3 206.645.2 17.5 13.5 29.3 CH 3 206.336.4 7.6 28.8 CH n 202.0 13.4 22.1 23.9 43.3 205.1 30.2 C O CH n 209.3 35.3 7.3 35.3 CH 3 13 CMR Use table to identify this compound

17. 0.93 1.35 1.59 2.42 9.76 400 MHz PMR Spectrum (from Chem 220, corrected with  from SDBS#10637)SDBS#10637 20 Hz J = 1.8 Hz J = 6.8 Hz same compound

18. Carbonyl Reactivity O Nu 1)Nucleophilic Addition (Bürgi-Dunitz Angle) Chapter 16 O Nu O (C=C prefers “Electrophilic” addition) 2) Nucleophilic Substitution of “Acid Derivatives” (A/D, like Aromatic) Chapter 18 L L ** H+H+ especially interesting for alcohol synthesis Nu = “R - ” (e.g. CH 3 Li) Nu = “H - ” (e.g. LiAlH 4 ) Secs. 16.13,16.16

19. HO Hydrate (gem-diol) RO Hemiacetal (  Acetal) RNH Carbinolamine (  Imine) HOSO 2 Bisulfite addition product NC Cyanohydrin etc. Secs. 16.6-16.11 Carbonyl Reactivity O H A B 3) Electrophilic Addition n (acid catalysis) O H (Easier than for C=C) O H 4) Allylic Rearrangement Ketone to Enol O H A A O H A O 5)  Substitution (Electrophilic)  -proton Nu Chapter 19 H then Nucleophile HO Nu the enol is a carbon nucleophile

20. Enols, Enolates and Enolization O >10 13 OH -3 O H O O 93 O O pK a 19 K enol formation 5  10 -9 O H (ketone ~11 kcal below enol) (ketone  enol help from conjugation, H-bonding) (ketone >17 kcal above enol help from aromaticity) pK a = 10 (anion only ~13 kcal/mol above phenol) H B (base catalysis) Chapter 19 pK a ~11!

21. RCOOH Reactions (Chapter 17) O H R C O H substitution at  -C substitution at C R substitution at O R addition A Nu

22. Mechanism for Acid-Catalyzed Hydrolysis of Acetal RO CH 2 + H HOH : : RO CH 2 + HROH RO-CH 2 + HO RO CH 2 + H First remove RO, and replace it by HO. HO RO CH 2 Now remove second RO, then H (from HO) + H : HO RO CH 2 + H RO=CH 2 + cation unusually stable; thus easily formed ROH H-O-CH 2 + O=CH 2 ROH RO CH 2 O H H  : Overall Transformation: H 2 O + Acetal Carbonyl + 2 ROH H+H+ (pp. 785-787) (hemiacetal) Good News: Much of this is review! e.g. secs. 16.9-16.10

23. Ph 3 C Propeller Conformation Ph Ph 3 C Mirror Conformation Ph Ph 3 C - Ph Two Mirrors rotated a bit

24. End of Lecture 64 April 1, 2011 Copyright © J. M. McBride 2011. Some rights reserved. Except for cited third-party materials, and those used by visiting speakers, all content is licensed under a Creative Commons License (Attribution-NonCommercial-ShareAlike 3.0).Creative Commons License (Attribution-NonCommercial-ShareAlike 3.0) Use of this content constitutes your acceptance of the noted license and the terms and conditions of use. Materials from Wikimedia Commons are denoted by the symbol. Third party materials may be subject to additional intellectual property notices, information, or restrictions. The following attribution may be used when reusing material that is not identified as third-party content: J. M. McBride, Chem 125. License: Creative Commons BY-NC-SA 3.0