1 / 40

ALKYNES - Chapter 7

ALKYNES - Chapter 7. nomenclature - ( chapt 5 ) , structure, classification acidity of terminal acetylenes - ( chapt 4 ) alkylation prep - dehydrohalogenation (-2HX) or double  -elimination reduction - H 2 /M (chapt 6) and chemical hydroboration (chapt 6) - protonation

comfort
Télécharger la présentation

ALKYNES - Chapter 7

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. ALKYNES - Chapter 7 nomenclature - (chapt 5), structure, classification acidity of terminal acetylenes - (chapt 4) alkylation prep - dehydrohalogenation (-2HX) or double -elimination reduction - H2/M(chapt 6) and chemical hydroboration (chapt 6) - protonation - oxidation (hydration) enol-keto tautomerism addition of Hg++,HX, X2, H2O (chapt 6) synthesis (chapts 6) ss25 18 [blue- chemistry from previous chapters]

  2. Chapter 7 synthesis nomenclature - structure, classification acidity of terminal acetylenes ) alkylation -elimination reduction - H2/M & chemical hydroboration - protonation - oxidation enol-keto tautomerism addition: Hg++/H2O,HX, X2 synthesis but first ……

  3. Chapter 7 synthesis nomenclature - structure, classification acidity of terminal acetylenes ) alkylation -elimination reduction - H2/M & chemical hydroboration - protonation - oxidation enol-keto tautomerism addition: Hg++/H2O,HX, X2 synthesis

  4. H C C H R C C R' acetylene, ethyne Structure - two general types (1) internal - R and R’ = alkyl, Aryl, etc. (2) terminal - R = alkyl, Aryl, etc. <-- creates additional chemistry 8,28

  5. R C C R’ Alkyne Nomenclature Common: alkyl alkyl' acetylene

  6. Nomenclature: IUPAC - longest chain containing the most important functional group(s) = root #-alkyne 4-chloro-6-cyclohexyl-5-methyl-2-hexyne add substituents with #’s

  7. 90o angle  bond to  orbitals)ß C R C R’ Acetylene - linear geometry - sp hybridization 180o bond angles R-C-C-R’  -bond 180o bond angle

  8. Name: ______________ seat: ____ Write the product(s) of the following reactions.

  9. H H H H H C C C H > CH C > C C 3 CH 3 CH H 3 H H pKa = 50 pKa = 44 H-Csp3 H-Csp2 The more s-character,the moreacidic the C-H bond 50% 33% 25% Acidity of organic compounds pKa = 25 H-Csp Why ? recall chapter 4

  10. also -NH2 H-NH3 Relative basicity (acidity)

  11. Acid-Base reactions organometallic reagent (15)

  12. last Thursday: Acid-Base reactions R' = alkyl = D

  13. Alkylation of Acetylides Recall RX type: substitution acetylide anions undergo substitution rx with 1o alkyl halides form new C-C bonds termed “alkylation”

  14. How do we make the anions of acetylenes? Alkylation of Acetylides

  15. Alkylation of Acetylides

  16. Acetylide anions - 2°and3° halides: -eliminates (strong base, reverse of addition) Alkylation of Acetylides no alkylation 2°R-X

  17. Preparation: Dehydrohalogenation (-2 HX) two -eliminations 2 arrangements of diBrs => same acetylene

  18. Preparation: Dehydrohalogenation (-2 HX) two -eliminations 2 arrangements of diBrs => same acetylene

  19. Preparation: Dehydrohalogenation (-2 HX) two -eliminations 2 arrangements of diBrs => same acetylene

  20. two -eliminations NOTE! alkenes are sources of diBrs 2 arrangements of diBrs => same acetylene Preparation: Dehydrohalogenation (-2 HX)

  21. Reactions - several like C=C - additions A. Reduction - addition of hydrogen syn addition (2x)

  22. Reactions - several like C=C - additions A. Reduction - addition of hydrogen With choice of catalyst - stop at olefin (add 1 eq H2). [Lindlar cat.] syn addition (2x)

  23. H C H Nao 3 H C C C CH C C 3 3 NH3 (liq.) CH H 3 ether (cosolvent) “mechanism” -Na donates e’s, know rx as prep for trans olefins Chemical reduction of a triple bond. trans olefin for internal acetylenes

  24. Acetylene chemistry - recall olefin chemistry R = H, alkyl

  25. Hydroboration of an internal alkyne terminal

  26. Terminal acetylene hindered borane adds once di-sec-isoamylborane or HB(sia)2

  27. Terminal acetylene hindered borane adds once di-sec-isoamylborane or HB(sia)2 tautomerism H+ transfer (O to C)

  28. ketone R' BH R' R' 2 O C H O C BH 2 2 C 2 + C H C NaOH H C H R R R H keto enol internal with oxidation - ketone

  29. regiochemistry

  30. enol-keto tautomerism H+ transfer C  O from HB/[O] Hg+2/H2O other rxs mechanism e(-) arrows or

  31. Hydration of acetylenes terminal yne - HBR2/[O] aldehyde - Hg++/H2O  ketone internal yne - “either”  ketone(s)

  32. R' Br R' Br R' Br C Br C 2 C Br 2 1 eq. C 1 eq. C C Br or XS Br R R R Br R' R' R' X C C C X X X C C C R R X R X electrophilic additions Br2 / Cl2 Assume bromonium (chloronium) ion ( like alkene X2 addition ) Mechanism for 1st addition of X2

  33. R' Br R' Br R' HBr C HBr C C Br 1 eq. C 1 eq. C C H or XS H H H H H R' C 2o-vinyl R+ C H H addition of HX vinyl bromide

  34. R' R' Br Br R' C HBr HBr C C Br C 1 eq. 1 eq. C C H or XS H H H H H R' Br R' Br C C Br(-) C C H H H H H H H Br R' C 1o carbocation and no resonance! C H H addition of HX - second addition 2o carbocation with resonance

  35. How could the vinyl bromide be converted into the Z-olefin? Use any number of reactions but show all necessary reagents and expected products of each step. how? a. H2/Lindlar(cat.) how? Na+-NH2 or b. (1)BH3,(2)AcOH/∆

  36. convert 2-bromopropene to 2-hexanone

  37. compare carbon skeleton functional groups convert 2-bromopropene to 2-hexanone

  38. compare carbon skeleton functional groups

  39. other way?

More Related