The document discusses elimination reactions where a substrate loses a small group like HCl, H2O or Cl2 during reaction to form products. It specifically discusses E2 and E1 elimination reactions of alkyl halides with strong or weak bases. E2 reactions are concerted single step reactions that are stereospecific and regioselective. E1 reactions proceed through a carbocation intermediate in two steps, are not stereospecific but are regioselective following Zaitsev's rule. The rate and mechanism depends on the concentration of base, structure of substrate and leaving group. Hofmann elimination reactions give the least substituted alkene as the major product when the leaving group is bulky like trimethylammonium.
Teori orbital molekul merupakan teori yang paling lengkap karena menyangkut interaksi elektrostatik dan interaksi kovalen . Berdasarkan teori orbital molekul, pada pembentukkan senyawa kompleks, orbital-orbital pada atom pusat dengan orbital-orbital dari ligan saling berinteraksi membentuk orbital-orbital molekul baru. Berdasarkan pedekatan linier, orbital-orbital molekul senyawa kompleks dianggap merupakan kombinasi linier dari orbital-orbital atom pusat dan orbital-orbital ligan. Perbedaan energy antara orbital-orbital atom pusat dengan ligan dapat diabaikan oleh karena itu dalam menggambarkan orbital molekul senyawa kompleks cukup digambarkan dengan orbital-orbital valensinya
makalah yang menjelaskan tata nama dan klasifikasi alkil halida, sifat-sifat alkil halida, reaksi substitusi dan eliminasi, reaksi SN-1 dan SN-2, dan yang terakhir reaksi E1 dan E2.
Teori orbital molekul merupakan teori yang paling lengkap karena menyangkut interaksi elektrostatik dan interaksi kovalen . Berdasarkan teori orbital molekul, pada pembentukkan senyawa kompleks, orbital-orbital pada atom pusat dengan orbital-orbital dari ligan saling berinteraksi membentuk orbital-orbital molekul baru. Berdasarkan pedekatan linier, orbital-orbital molekul senyawa kompleks dianggap merupakan kombinasi linier dari orbital-orbital atom pusat dan orbital-orbital ligan. Perbedaan energy antara orbital-orbital atom pusat dengan ligan dapat diabaikan oleh karena itu dalam menggambarkan orbital molekul senyawa kompleks cukup digambarkan dengan orbital-orbital valensinya
makalah yang menjelaskan tata nama dan klasifikasi alkil halida, sifat-sifat alkil halida, reaksi substitusi dan eliminasi, reaksi SN-1 dan SN-2, dan yang terakhir reaksi E1 dan E2.
Unit 8 - Information and Communication Technology (Paper I).pdfThiyagu K
This slides describes the basic concepts of ICT, basics of Email, Emerging Technology and Digital Initiatives in Education. This presentations aligns with the UGC Paper I syllabus.
A Strategic Approach: GenAI in EducationPeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
Palestine last event orientationfvgnh .pptxRaedMohamed3
An EFL lesson about the current events in Palestine. It is intended to be for intermediate students who wish to increase their listening skills through a short lesson in power point.
Honest Reviews of Tim Han LMA Course Program.pptxtimhan337
Personal development courses are widely available today, with each one promising life-changing outcomes. Tim Han’s Life Mastery Achievers (LMA) Course has drawn a lot of interest. In addition to offering my frank assessment of Success Insider’s LMA Course, this piece examines the course’s effects via a variety of Tim Han LMA course reviews and Success Insider comments.
Model Attribute Check Company Auto PropertyCeline George
In Odoo, the multi-company feature allows you to manage multiple companies within a single Odoo database instance. Each company can have its own configurations while still sharing common resources such as products, customers, and suppliers.
Operation “Blue Star” is the only event in the history of Independent India where the state went into war with its own people. Even after about 40 years it is not clear if it was culmination of states anger over people of the region, a political game of power or start of dictatorial chapter in the democratic setup.
The people of Punjab felt alienated from main stream due to denial of their just demands during a long democratic struggle since independence. As it happen all over the word, it led to militant struggle with great loss of lives of military, police and civilian personnel. Killing of Indira Gandhi and massacre of innocent Sikhs in Delhi and other India cities was also associated with this movement.
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...Levi Shapiro
Letter from the Congress of the United States regarding Anti-Semitism sent June 3rd to MIT President Sally Kornbluth, MIT Corp Chair, Mark Gorenberg
Dear Dr. Kornbluth and Mr. Gorenberg,
The US House of Representatives is deeply concerned by ongoing and pervasive acts of antisemitic
harassment and intimidation at the Massachusetts Institute of Technology (MIT). Failing to act decisively to ensure a safe learning environment for all students would be a grave dereliction of your responsibilities as President of MIT and Chair of the MIT Corporation.
This Congress will not stand idly by and allow an environment hostile to Jewish students to persist. The House believes that your institution is in violation of Title VI of the Civil Rights Act, and the inability or
unwillingness to rectify this violation through action requires accountability.
Postsecondary education is a unique opportunity for students to learn and have their ideas and beliefs challenged. However, universities receiving hundreds of millions of federal funds annually have denied
students that opportunity and have been hijacked to become venues for the promotion of terrorism, antisemitic harassment and intimidation, unlawful encampments, and in some cases, assaults and riots.
The House of Representatives will not countenance the use of federal funds to indoctrinate students into hateful, antisemitic, anti-American supporters of terrorism. Investigations into campus antisemitism by the Committee on Education and the Workforce and the Committee on Ways and Means have been expanded into a Congress-wide probe across all relevant jurisdictions to address this national crisis. The undersigned Committees will conduct oversight into the use of federal funds at MIT and its learning environment under authorities granted to each Committee.
• The Committee on Education and the Workforce has been investigating your institution since December 7, 2023. The Committee has broad jurisdiction over postsecondary education, including its compliance with Title VI of the Civil Rights Act, campus safety concerns over disruptions to the learning environment, and the awarding of federal student aid under the Higher Education Act.
• The Committee on Oversight and Accountability is investigating the sources of funding and other support flowing to groups espousing pro-Hamas propaganda and engaged in antisemitic harassment and intimidation of students. The Committee on Oversight and Accountability is the principal oversight committee of the US House of Representatives and has broad authority to investigate “any matter” at “any time” under House Rule X.
• The Committee on Ways and Means has been investigating several universities since November 15, 2023, when the Committee held a hearing entitled From Ivory Towers to Dark Corners: Investigating the Nexus Between Antisemitism, Tax-Exempt Universities, and Terror Financing. The Committee followed the hearing with letters to those institutions on January 10, 202
How to Make a Field invisible in Odoo 17Celine George
It is possible to hide or invisible some fields in odoo. Commonly using “invisible” attribute in the field definition to invisible the fields. This slide will show how to make a field invisible in odoo 17.
Biological screening of herbal drugs: Introduction and Need for
Phyto-Pharmacological Screening, New Strategies for evaluating
Natural Products, In vitro evaluation techniques for Antioxidants, Antimicrobial and Anticancer drugs. In vivo evaluation techniques
for Anti-inflammatory, Antiulcer, Anticancer, Wound healing, Antidiabetic, Hepatoprotective, Cardio protective, Diuretics and
Antifertility, Toxicity studies as per OECD guidelines
Read| The latest issue of The Challenger is here! We are thrilled to announce that our school paper has qualified for the NATIONAL SCHOOLS PRESS CONFERENCE (NSPC) 2024. Thank you for your unwavering support and trust. Dive into the stories that made us stand out!
2. suatu reaksi dimana substrat kehilangan unsur dari molekul kecil seperti HCl, H 2 O atau Cl 2 selama reaksi pembentukan produk REAKSI ELIMINASI - HCl C C H Cl C C
3. REAKSI ELIMINASI Alkil halida + basa kuat dan panas Alkohol + asam kuat dan panas Kehilangan HCl Kehilangan H 2 O DUA CONTOH E2 E1
4. + HCl - HCl ELIMINASI LAWAN DARI ADISI Kondisi basa + panas Kondisi asam interkonversi dari alkil halida dan alkena ALKIL HALIDA ALKENA C H 3 C H 2 C H C H 3 C l C H 3 C H C H C H 3 HCl pekat NaOH + panas
5. + H 2 O - H 2 O Kondisi asam kuat + panas Kondisi asam encer 2-6 M H 2 SO 4 H 2 SO 4 pekat interkonversi dari alkohol dan alkena ALKOHOL ALKENA ELIMINASI LAWAN DARI ADISI C H 3 C H C H C H 3 C H 3 C H 2 C H C H 3 O H
7. BASA KUAT NaOH water Basa pelarut yang diijinkan KOH water, MeOH, EtOH NaOR ROH (same R group) NaNH 2 NH 3 (liq) -33 o C Digunakan untuk reaksi eliminasi Halida (RX) tidak larut dalam air, tetapi larut dalam alkohol, Karena itu KOH atau NaOR dalam alkohol sering digunakan
9. SUMMARY TO DATE BASA KUAT Dibutuhkan REGIOSELECTIVE Mengikuti aturan Zaitsev Rule ) - membentuk alkena yang lebih tersubstitusi STEREOSPECIFIC -H dan X harus ANTI-COPLANAR REAKSI ELIMINASI ALKIL HALIDA Panas Selalu dibutuhkan
10. MEKANISME SERENTAK = HANYA SATU TAHAP Semua ikatan terputus dan terbentuk tanpa pembentukan suatu intermediet Eliminasi Bimolekular Basa kuat alkil halida E 2
11. Orde Reaksi Molekularitas Tahap Penentu Kecepatan Keadaan Transisi Kompleks Teraktivasi Jumlah eksponen dari konsentrasi pada persamaan kecepatan Jumlah spesi yang ada pada tahap penentu kecepatan Tahap paling lambat dalam rangkaian reaksi Energi tertinggi dalam profil energi suatu reaksi Spesi yang ada pada keadaan transisi
13. mekanisme Kompleks teraktivasi ELIMINASI E2 Serentak: semua terjadi pada satu waktu, tanpa suatu intermediet C H C H B r H B :
14. Reaksi Serentak (Satu Tahap) product starting material Keadaan Transisi TS Energi Aktivasi Ea Panas Reaksi H E N E R G Y
15. C C H Br R R H H O CH 3 : .. .. .. .. .. : : Serangan basa pada hydrogen- memulai reaksi sp 3 sp 3 Ketika elektron ini memasuki orbital tetangga, maka proses ini akan mendorong pasangan ikatan keluar The critical event is the removal of the -H.
16. C C H Br R R H H O CH 3 .. .. .. : : .. . . Pembentukan ikatan rangkap dan Kehilangan atom bromida 2p 2p
17. REAKSI ADALAH ELIMINASI- Gugus fungsi terikat Ke karbon- . -carbon -carbon Hydrogen - terikat Ke karbon- . Karena hydrogen- hilang dalam reaksi ini Maka disebut Eliminasi- . Reagent = Basa kuat
18. C C C l H B: Basa mengambil HYDROGEN- C C C l H B : : .. : : .. .. MEKANISME
20. APA YANG TERJADI JIKA LEBIH DARI SATU HYDROGEN- ? ’ MANA YANG HILANG ?
21. ELIMINASI ADALAH REGIOSELECTIVE ’ -H ’ -H Produk Mayor adalah Yang punya energi terendah 2-bromobutana 2-butena 1-butena major product 81 % minor product 19 %
22. major product minor product ’’ ’ ’’ = ’ MORE REGIOSELECTIVITY identical to -product ’’ 1-chloro-1-methylcyclohexane 1-methylcyclohexene methylenecyclohexane 1-methylcyclohexene 3 kemungkinan Kehilangan hydrogen-
23. -27.8 -25.4 H +H 2 +H 2 kcal mole METHYLCYCLOHEXENE ISOMERS Both are hydrogenated to the same product therefore their energies may be compared. methylcyclohexane RECALL
24. ATURAN SAYTZEV Reaksi yang memberikan alkena yang lebih tersubstitusi (energi terendah) sebagai produk mayor
25. monosubstitusi trisubstitusi disubstitusi decreasing energy tetrasubstitusi Peningkatan substitusi ISOMER LEBIH TERSUBSTITUSI LEBIH STABIL ISOMER ALKENA Perbedaan posisi dari ikatan rangkap cis trans 1,1- 1,2- 1,2- H H R H H H R R R H R H H R R H R H R R R R R R
26. major product 81 % minor product 19 % major product minor product APLIKASI ATURAN ZAITZEV DISUBSTITUSI TRISUBSTITUSI DISUBSTITUSI MONOSUBSTITUSI 2-bromobutane 1-chloro-1-methylcyclohexane
28. STEREOKIMIA TWO EXTREME POSSIBILITIES FOR THE ELIMINATION PROCESS C C H Cl syn elimination C C H Cl anti elimination tidak umum terjadi sering terjadi H H Cl Cl anti-coplanar
29. 1-Bromo-2-methylcyclohexane major product Zaitsev The expected result (naïve) : minor The result actually depends on the stereochemistry of the starting material ( cis or trans ). drawn flat without stereochemistry
30. cis The elimination needs to have H and Br anti-coplanar plus a small amount of major product (Zaitsev) Br CH 3 THE CIS STEREOISOMER The other chair won’t work. Why? trans shown on next slide
31. trans only product Br CH 3 THE TRANS STEREOISOMER The other chair won’t work. Why? no methylcyclohexene is formed
32. ALKIL HALIDA + BASA LEMAH (SOLVOLYSIS) E1 Pemindahan hydrogen- menjadi sukar tanpa basa kuat, Sehingga reaksi berjalan denngan mekanisme berbeda
33. Reaksi Eliminasi E1(dua tahap) + : X slow fast rate = k [RX] karbokation 3 o > 2 o > 1 o Bekerja baik dalam pelarut polar Pembentukan ion unimolecular Tahap 1 Tahap 2 Basa lemah
34. starting material product Ea 1 Ea 2 H intermediate TS 2 TS 1 PROFIL ENERGi two step reaction E N E R G Y step 1 step 2 carbocation slow E1
36. C X C H C X C H C C H C C H + + Carbocation is sp 2 hybridized ( planar ) and can react from either side. These two carbocations are equivalent by rotation and by symmetry. anti syn REAKSI E1 TIDAK STEREOSPECIFIC rotation rate of C-C rotation = 10 10 to 10 12 / sec ( karbokation terbuka adalah palanar dan bisa berputar) Elimination can be either syn or anti .
38. REAKSI E1 ADALAH REGIOSELECTIVE MENGIKUTI ATURAN ZAITSEV major minor 0.001 M KOH / EtOH tertiary trisubstitusi (stereochemistry is not a problem as in E2) disubstitusi very dilute base Zaitsev
42. [RX] constant, [B] increasing Rate rate = k 1 [RX] E1 rate = k 2 [RX] [B] E2 KECEPATAN DENGAN PENINGKATAN KONSENTRASI BASA second order first order E1 terjadi pada Konsentrasi basa rendah E2 pada konsentrasi basa lebih tinggi
43. [RX] constant, [Base] increasing Rate PENGARUH KONSENTRASI BASA PADA REAKSI E1/E2 secondary RX, k’ tertiary RX, k’’ primary RX, k k 1 [RX] E1 For E1 elimination : k’’ (tertiary) > k’ (secondary) > k (primary). k 2 [RX] [B] E2 1 1 1 At high base concentration E1 never has a chance. At low base concentration E2 is nonexistent
44. secondary RX, k’ tertiary RX, k’’ primary RX, k [RX] constant, [B] Rate k 1 [RX] E1 k 2 [RX] [B] E2 For E2 elimination : line slopes k 2 differ for 1 o ,2 o ,3 o . Different substrates react at different rates, primary secondary tertiary 1 1 2 k 2 k’ k’’ 2 PENGARUH KONSENTRASI BASA PADA REAKSI E1/E2
45. Obviously for E1 which forms a carbocation intermediate kecepatan : tertiary > secondary > primary > methyl But this same order holds for E2 also. STRUKTUR SUBSTRAT R-C-X R R R-C-X R H R-C-X H H primary secondary tertiary tertiary has more -hydrogens EtO - more opportunites for reaction
46. Jika basa kuat ada pada konsentrasi tinggi, atau substrat adalah halida 1 0 , reaksi berjalan E2 KAPAN MEKANISME E1 TERJADI ??? E1 terjadi hanya: 1) Pada konsentrasi basa rendah 2) Dengan solvolisis (pelarut adalah basa) 3) Dengan substrat tersier dan beresonasi (alkil halida)
47. Mekanisme E2 Mekanisme E1 Basa kuat Kons basa tinggi. Basa lemah Kons basa rendah ALKIL HALIDA + BASA solvolysis Harus membentuk karbokation baik or Membutuhkan anti-coplanar (pelarut basa) stereospecific regioselective not stereospecific regioselective
48. EXAMPLES N a O E t E t O H E t O H 6M K O H 0.01 M E2 E1 rate = k [RBr] rate = k [RBr] [OEt] C H B r C H 3 C H B r C H 3 C H C H 2 C H C H 3 + .. :O E t ..
50. JENIS PENATAAN ULANG KARBOKATION Perpindahan metil Perpindahan hidrogen Perpindahan fenil Gugus pindah dengan elektron ikatannya Pergeseran 1,2-metil Pergeseran 1,2-hydrogen Pergeseran 1,2-phenyl
51. methyl shift protonation loss of H 2 O loss of H + Penataan ulang – pergesaran 1,2-METIL H 2 SO 4
52. Kenapa terjadi penataan ulang ? Ion sekunder Ion tersier Karbokation menata ulang Untuk mencapai energi terendah Energi karbokation 3 o < 2 o < 1 o < CH 3 + energy decrease lowest highest
53. Gugus mana yang pindah ? tertiary benzylic Gugus yang memberikan Karbokation terbaik yang Akan pindah yes secondary benzylic secondary no no Kompetisi antara H atau Me atau Ph ? BINGO !
54. DO YOU HAVE A CARBOCATION? CAN YOU FORM A BETTER CARBOCATION ? STOP E X R E M E R E G N A D STOP - LOOK - THINK ALWAYS EVALUATE FOR A REARRANGEMENT
56. ATURAN HOFMANN When you have a bulky leaving group like -N(CH 3 ) 3 + the least-substituted alkene will be the major product. BULKY = Branched at the first atom attached to the chain OTHER GROUPS FOLLOW THE ZAITSEV RULE trimethyl ammonium dimethyl sulfonium chain chain Big is not the same as bulky.
57. HOFMANN ELIMINATION Hofmann found that when the leaving group was -N(CH 3 ) 3 + E2 elimination reactions gave the least-substituted alkene. 95% 5% 31% 69% Hofmann Zaitsev
58. 31% 69% 30% 70% 48% 52% 87% 13% 98% 2% HOFMANN ZAITSEV EFFECT OF INCREASING SUBSTITUENT BULK ( cis + trans ) E2 Big is not the same as bulky.
59. C C C C C H 3 X H H HOFMANN ZAITSEV cis trans ( all H equivalent ) bulky groups cause crowding and give Hofmann products ANALYSIS OF 2-SUBSTITUTED PENTANE ELIMINATIONS less crowding in this area of the molecule
60. cis trans ZAITSEV PRODUCTS HOFMANN PRODUCT N(CH 3 ) 3 CH 2 CH 2 CH 3 H N(CH 3 ) 3 CH 3 CH 2 CH 3 H CH 3 CH 2 CH 3 N(CH 3 ) 3 H most steric crowding no steric crowding less steric crowding H H H H H H H WOULD MAKE WOULD MAKE NOT FORMED FORMED
61. BULKY BASES ALSO INCREASE HOFMANN PRODUCT 81% 19% 47% 53% ZAITSEV HOFMANN bulky base t -butoxide methoxide
62. BULKY -SUBSTITUENTS 80% 20% 79% 21% 14% 86% ZAITSEV HOFMANN NaOEt NaOEt NaOEt What constitutes bulky? NO NO YES t-butyl is bulky ! a methyl group is not bulky even two or three are not bulky
63. crowded less crowded THE ELIMINATION MOVES TO A LESS CROWDED REGION 86% 14% spacer REACTIVE CONFORMATIONS crowding crowding H H CH 3 Br C CH 3 CH 3 CH 3 CH 3 C H H CH 3 H Br CH 2 CH 3 CH 3 CH 3
65. Br CH 3 CH 3 CH 3 N(CH 3 ) 3 + I - CH 2 Br CH 3 CH 2 CH 3 NaOEt EtOH / KOH EtOH / NaOtBu tBuOH / + ~90% ~90% ~60/40% Zaitsev Hofmann NORMAL BULKY LEAVING GROUP BULKY BASE HOW THE VARIOUS FACTORS AFFECT THE OUTCOME Bulky base alone not as effective as bulky leaving group Prototypical “Hofmann” elimination Bromine is big, not bulky
66. Br CH 3 CH 3 N(CH 3 ) 3 + I - CH 2 NaOtBu tBuOH / BULKY BASE & LEAVING GROUP ~100% Hofmann tBu CH 3 NaOEt EtOH / BULKY -SUBSTITUENT HOW THE VARIOUS FACTORS AFFECT THE OUTCOME ( CONTINUED ) tBu either cis or trans to Br - same result H CH 2 tBu + no double bond here Double Whammy ! Favors Hofmann products Bulky base + bulky leaving group Use a bulky base here and ...
67. E2 REACTIONS DEVIATE FROM THE ZAITSEV RULE 1. If the favored -hydrogen can’t achieve anti-coplanar geometry. 2. If the double bond would form at a bridgehead. 3. If there is a bulky leaving group. 4. If there is a bulky base. 5. If there is a bulky -substituent. (see next slides)
70. K.I.S.S. alkyl halide + strong base + heat = E2 alkyl halide + solvent + heat (solvolysis) = E1 alcohol + strong acid + heat = E1 (acid assisted) typical situation for E1cb H next to C=O (easy to remove) X = strong base (difficult to break bond) Only E1 reactions have rearrangements (carbocations) Only E2 reactions require anti-coplanar -hydrogens THE MOST BASIC STUFF
71. E1cb E2 E1 E1 E1 acid assisted strong strong weak base base base “ solvolysis” Zaitsev if stereochem allows Zaitsev Zaitsev Zaitsev stereospecific anti-coplanar alkyl halides alcohols special special case - not common acidic neutral carbocation rearrangements concerted stepwise - carbocation requires: acidic H and poor leaving group stepwise - carbanion not stereospecific -elim. if no -H Hofmann if bulky groups THE BIG PICTURE
72. THERE IS A RANGE OF DIFFERENT MECHANISMS FOR -ELIMINATION REACTIONS SUMMARY
73. E1cb E2 E1 E1 E1 acid assisted strong strong weak base base base “ solvolysis” Zaitsev if stereochem allows Zaitsev Zaitsev Zaitsev stereospecific anti-coplanar alkyl halides alcohols special special case - not common acidic neutral carbocation rearrangements concerted stepwise - carbocation COMPARISON OF -ELIMINATION MECHANISMS requires: acidic H and poor leaving group stepwise - carbanion not stereospecific
74. K.I.S.S. alkyl halide + strong base + heat = E2 alkyl halide + solvent + heat (solvolysis) = E1 alcohol + strong acid + heat = E1 (acid assisted) typical situation for E1cb H next to C=O (easy to remove) X = strong base (difficult to break bond) Only E1 reactions have rearrangements (carbocations) Only E2 reactions require anti-coplanar -hydrogens