11-08 - 11/8/2010 Propose a structure for compound X based...

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Unformatted text preview: 11/8/2010 Propose a structure for compound X based on the following data: Molecular formula = C6H12 Ozonolysis of X gave two compounds, Y and Z with the formula: Y = CH2O and Z = C5H10O The nmr spectrum of Z is given below: Choose a structure for compound A based on the following data: Molecular formula = C6H12 Ozonolysis of X gave two compounds, Y and Z with the formula: Y = CH2O and Z = C5H10O The nmr spectrum of Z is given below: A B C D E F What experiments could be done to determine the structure of compound X? A. Record their infrared spectra. B. Determine their solubility in water. C. Synthesize each of these compounds and compare their data to compound X. What are the important elements of a proton nmr spectrum? 1. Multiplicities of an absorption. number peaks from vicinal coupling = n + 1 n = number of vicinal hydrogens (adjacent) Which absorption is due to the two equivalent methyls? 1 2 A B C Z more than 5 B C A What are the important elements of a proton nmr spectrum? 1. Multiplicities of an absorption. number peaks from vicinal coupling = n + 1 n = number of vicinal hydrogens (adjacent) Which absorption is due to the two equivalent methyls? What are the important elements of a proton nmr spectrum? 1. Multiplicities of an absorption. number peaks from vicinal coupling = n + 1 n = number of vicinal hydrogens (adjacent) Which absorption is due to the single methyl group? B C Z A Z A B C 1 11/8/2010 What are the important elements of a proton nmr spectrum? 1. Multiplicities of an absorption. number peaks from vicinal coupling = n + 1 n = number of vicinal hydrogens (adjacent) How many absorptions are due to the single hydrogen? What are the important elements of a proton nmr spectrum? 1. Multiplicities of an absorption (spin-spin coupling). number peaks from vicinal coupling = n + 1 n = number of vicinal hydrogens (adjacent) 2. The position of the absorption (chemical shift). A=1 B=3 C=5 B=7 C=9 multiplicity multiplicity position The Interaction of Light with Matter The Interaction of Light with Matter short wavelength electromagnetic spectrum long wavelength Choose the true statements about electromagnetic absorptions. 2. Ultraviolet absorptions (uv) cause the transition between two electronic states. Typical electromagnetic absorptions. infrared: electronic nuclear magnetic resonance: 1. Infrared absorptions (ir) cause the transition between two vibrational states. 3000 cm-1 300 nm 300 MHz energy 3. Light with a wavelength of 1 meter is higher in energy than light with a wavelength of 10-9 meters. A. 1+2+3 short wavelength B. 1+2 C. 1+3 D. 1 E. 2 F. 3 300 nm = 400 kJ/mol 3000 cm-1 = 36 kJ/mol 300 MHz = 0.00012 kJ/mol electronic short short wavelength ir nmr long wavelength electromagnetic spectrum long wavelength electromagnetic spectrum ultraviolet infrared radio 2 11/8/2010 infrared: electronic nuclear magnetic resonance: antibonding antibonding 3000 cm-1 300 nm 300 MHz infrared: electronic nuclear magnetic resonance magnetic magnetic moment of a hydrogen nucleus magnetic field field energy bonding electronic ir nmr long wavelength short wavelength electromagnetic spectrum ultraviolet electromagnetic radiation 14 infrared radio Nuclear Magnetic Resonance spectroscopy probes the electronic environment of a molecular structure. HO HO O Nuclear Magnetic Resonance. N In a magnetic field how do most of the hydrogen nuclei These magnetic moments have no orient their magnetic moments? orientation. A. parallel to the magnetic field. B. perpendicular to the magnetic field. N O OH OH O O O O O OH OH O C. their magnetic moments will disappear in a magnetic field. D. their magnetic moments show no organization in a magnetic field. O O H H H H rapamycin C51H79NO13 15 S Nuclear Magnetic Resonance. N In a magnetic field how do most of the hydrogen nuclei orient their magnetic moments? A. parallel to the magnetic field. B. antiparallel to the magnetic field. C. perpendicular to the magnetic field. D. their magnetic moments show no organization in a magnetic field. S 17 Nuclear Magnetic Resonance. HO HO In a magnetic field the hydrogen nuclei orient parallel and antiparallel to the magnetic field. N O N O OH OH O O O O O OH OH O O O H H S rapamycin C51H79NO13 18 3 11/8/2010 Nuclear Magnetic Resonance. N Will the wave length of electromagnetic for a nuclear spin transitions be capable of breaking chemical bonds? N A. Yes B. No λ ∆E ∆E the molecules absorb light of an energy equal to the energy difference between the two spin states. energy S 19 energy S 1 energy energy ~ frequency = υ = — frequency λ ∆E = 300 MHz = 300,000,000 ∆E = 0.12 J/mol ∆E(H-H bond) = 436,000 J/mol 20 Magnetic Resonance Imaging (MRI) N Magnetic Resonance Imaging (MRI) N ∆E energy S 1 frequency frequency = υ = — λ energy S 21 22 What chemical is everywhere in our bodies? H H O N water in different tissues has a different relaxation rates (T1). N MRI measures differences in relaxation rates. (images) MRI N MRI N ∆E S S 23 S S 24 4 11/8/2010 MRI measures differences in relaxation rates. (images) When we think the brain requires glucose and oxygen. The oxygen is attached to Fe (hemoglobin) which can dramatically affect the relaxation rate of water. NMR spectroscopy (MRS) measures differences in nuclear spin transition energies. (molecular structure) fMRI glucose + OO Fe N N H H H N O H O NH NH H O H H H O O OH OH H diamagnetic energy S 25 ∆E ∆E O O H H HO H HO O H OO O O ∆E = 300,000,000 Hz S S 26 paramagnetic Is the frequency required to flip the magnetic moment of H2 (A) greater or (B) less than H1? A. greater N Does H1 experience a (A) stronger or (B) weaker magnetic field than H2? A. stronger N B. less N B. weaker N ∆E H1 H2 O H ∆E ∆E = 300,000,900 Hz S 27 ∆E H1 H2 O H ∆E ∆E = 300,000,900 Hz S 28 energy ∆E = 300,000,000 Hz S energy ∆E = 300,000,000 Hz S 5 ...
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