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8 . Alken a : Pembuatan dan Reaksi

8 . Alken a : Pembuatan dan Reaksi. Based on McMurry’s Organic Chemistry 6 th edition. Pembuatan Alkena : Reaksi Eliminasi. Alkena biasanya dibuat dengan cara: Dehydration Alkohol Tersier. Pembuatan Alkena : Reaksi Eliminasi. Dehydrohalogenation.

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8 . Alken a : Pembuatan dan Reaksi

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  1. 8. Alkena: Pembuatan dan Reaksi Based on McMurry’s Organic Chemistry 6th edition

  2. Pembuatan Alkena: Reaksi Eliminasi • Alkena biasanya dibuat dengan cara: • Dehydration Alkohol Tersier McMurry Organic Chemistry 6th edition Chapter 7 (c) 2003

  3. Pembuatan Alkena: Reaksi Eliminasi • Dehydrohalogenation McMurry Organic Chemistry 6th edition Chapter 7 (c) 2003

  4. 8.1 Preparation of Alkenes: A Preview of Elimination Reactions Dehidrohalogenasi McMurry Organic Chemistry 6th edition Chapter 6 (c) 2003

  5. Reaksi-reaksi alkena • Alkena bereaksi dengan banyak elektrofil menghasilkan produk melalui reaksi adisi • Menghasilkan alkohol (bila mengadisi H-OH) • Menghasilkan alkana (bila mengadisi H-H) • Menghasilkan halohidrin (bila mengadisi HO-X) • Menghasilkan dihalida (bila mengadisi X-X) • Menghasilkan halida (bila mengadisi H-X) • Menghasilkan diol (bila mengadisi HO-OH) • Menghasilkan siklopropana (bila mengadisi :CH2) McMurry Organic Chemistry 6th edition Chapter 6 (c) 2003

  6. 8.2 Adisi Halogen pada Alkena McMurry Organic Chemistry 6th edition Chapter 6 (c) 2003

  7. Mechanism • Step 1: Pembentukan bridgedbromonium ion intermediate • Step 2: Penyerangan ion halida dari arah yang berlawanan (oppositeside)dari cincin anggota tiga

  8. 8.3 Pembentukan Halohidrin Reagennya Br2atau Cl2 ) McMurry Organic Chemistry 6th edition Chapter 6 (c) 2003

  9. Mekanisme pembentukan Bromohidrin Step 1 Step 2 McMurry Organic Chemistry 6th edition Chapter 6 (c) 2003

  10. 8.4 Adisi air pada alkena: Oksimerkurasi/Reduksi McMurry Organic Chemistry 6th edition Chapter 6 (c) 2003

  11. Addition of Hg(II) and oxygen is anti & stereoselective McMurry Organic Chemistry 6th edition Chapter 6 (c) 2003

  12. Mechanism of Oxymercuration • 1. Electrophilic addition of Hg(OAc)2 produces mercurinium ion. • 2. Water acts as a nucleophile, attacks the more substituted carbon atom to form a C-O bond. • Acetate ion removes hydrogen, forming a neutral product, but the HgOAc is still attached. • NaBH4 reduces the HgOAc, replacing it with a hydrogen atom to form the alcohol product. McMurry Organic Chemistry 6th edition Chapter 7 (c) 2003

  13. 8.5 Adisi air pada alkena: Hidroborasi • Boran adalah asam Lewis yang mampu menerima elektron • Boran diadisi alkenamenghasilkan organoboran McMurry Organic Chemistry 6th edition Chapter 6 (c) 2003

  14. Orientasi dalam hidrasi melalui Hidroborasi • Regiokimianya berlawanandengan orientasi Markovnikov • OH terikat pada karbon dengan atom H paling banyak • H and OH add with syn stereochemistry, to the same face of the alkene (opposite of anti addition) McMurry Organic Chemistry 6th edition Chapter 6 (c) 2003

  15. Hidroborasi, Efek Elektronik memberikan Non-Markovnikov • More stable carbocation is consistent with steric preferences McMurry Organic Chemistry 6th edition Chapter 6 (c) 2003

  16. Mekanisme Hidroborasi McMurry Organic Chemistry 6th edition Chapter 7 (c) 2003

  17. 8.7 Reduksi Alkena: Hidrogenasi • Alkena bereaksi dengan H2dengan adanya katalis logam transisi menghasilkan alkana • commonly used catalysts are Pt, Pd, Ru, and Ni • Proses ini disebut reduksi katalitik (catalytic reduction)atau hidrogenasi katalitik (catalytic hydrogenation) McMurry Organic Chemistry 6th edition Chapter 6 (c) 2003

  18. Mechanism of Hydrogenation McMurry Organic Chemistry 6th edition Chapter 7 (c) 2003

  19. 8.8 Oksidasi alkena: Hidroksilasi dan Pemutusan • Hidroksilasi mengadisi OH pada kedua karbon C=C • Dikatalisis oleh osmium tetroksida • Stereokimia adisi adalah syn • Produknya adalah 1,2-dialkohol or diol (disebut juga glikol =glycol) McMurry Organic Chemistry 6th edition Chapter 6 (c) 2003

  20. Ozonolisis alkena McMurry Organic Chemistry 6th edition Chapter 6 (c) 2003

  21. Structure Elucidation With Ozone • Cleavage products reveal an alkene’s structure McMurry Organic Chemistry 6th edition Chapter 6 (c) 2003

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