+ OH X Nu X Nu Nu− X− NMR Benchtop NMR for Educational Experiments Y Y O O + H2O HO Y O O + N + N O O + HN Elimination Reaction Br 2 + N NH O + N O O O This experiment is designed to teach the practical aspects andOprinciples of the HO + + OH HO elimination reaction: H2SO4 2 X Nu + X− of reaction conditions. Isolation of organic compounds, effect X Nu Nu− Total experiment time: 1.5 hours in aqueous, 2 hours inYacetone Y The elimination reaction involves the reaction of a halogenalkane in the presence of heat and a base to produce an alkene. O HC OH + O CH O 3 3 H SO O 2,3-dibromo-3-phenylpropanoic An example is the elimination reaction of acid O to form 1-bromo-2-phenylethene that takes O O 2 4 + H2O + + + - N on the reaction + place OH via an E1 conditions. The reaction is performed in the presence of potassium HOor E2 reaction depending O - N N carbonate: X Nu X Nu− NH O OR O O Br + N + N O Br O HOO + N O H2N Br Y O + Br X− Br Y O Nu Br O + O + N H2N + NH can be used to measure the spectra of the starting material and reaction Pulsar™, a 60MHz benchtop NMR spectrometer + N - completed and no starting materials remain. The spectra of the starting material product confirming that the reaction has O O CH3 HC 2,3-dibromo-3 phenylpropanoic acid, along with the OH final phenylethene are shown in Figure 1. CH + product 1-bromo-2 3 3 + O Figure 1. From top to bottom: 2,3-dibromo-3-phenylpropanoic acid, 1-bromo-2-phenylethene spectra Br Br O OR OH Br HO + CH3 Br H3C Br CH3 O ! Br O OR Br HO Br ! Oxford Instruments Industrial Analysis It is clear from these spectra that there is no starting material present in the For more information please email: [email protected] spectrum of 1-bromo2-phenylethene. The UK Tubney Woods, Abingdon, Oxfordshire, OX13 5QX, UK Tel: +44 1865 393 200 1-bromo-2-phenylethene has tetramethylsilane (TMS) added as a chemical shift reference material showing China Floor 1, Building 60, No. 461 HongCao Road, Shanghai, 200233, PRC Tel: + 86 21 61273858 a peak at 0ppm chemical shift. The product formed can be either a cis- or transform of the compound Figure 2. Peaks in the spectrum of the reaction product due to cis (pink) and trans (blue) forms of the compound. dependent on the solvent chosen for the reaction. In Pulsar is a cryogen-free benchtop NMR spectrometer acetone the yield is almost that can easily be sited in the Undergraduate Chemistry 98% cis form. Whereas in laboratory allowing hands-on NMR for students. water the yield is 20% cis A simple to use software interface and standard sampling and 80% trans form of the compound. The peaks due to the different forms (trans using 5mm NMR tubes enables a high throughput of samples in a busy laboratory. peaks are highlighted in blue, cis peaks in pink) are shown in Figure 2. Contact us now for more information [email protected] for more information visit www.oxford-instruments.com 2273 This publication is the copyright of Oxford Instruments plc and provides outline information only, which (unless agreed by the company in writing) may not be used, applied or reproduced for any purpose or form part of any order or contract or regarded as the representation relating to the products or services concerned. Oxford Instruments’ policy is one of continued improvement. The company reserves the right to alter, without notice the specification, design or conditions of supply of any product or service. Oxford Instruments acknowledges all trademarks and registrations. © Oxford Instruments plc, 2014. All rights reserved. Part no: Pulsar/Expt10/02-14 As part of Oxford Instruments’ environmental policy this brochure has been printed on FSC paper India 11, Marwah’s Complex, Andheri East, Mumbai, 400072, India Tel: +91 22 4253 5100 Japan IS Building, 3-32-42, Higashi-Shinagawa, Shinagawa-ku, Tokyo, 140-0002, Japan Tel: +81 3 6732 8970 Singapore 10 Ubi Crescent 04-81, Ubi Techpark, Lobby E, Singapore, 408564, Singapore Tel: +65 6337 6848 USA 300 Baker Avenue, Suite 150, Concord, Mass 01742, USA Tel: +1 978 369 9933 www.oxford-instruments.com