11-12 - 11/12/2010 Propose a structure for a compound with...

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Unformatted text preview: 11/12/2010 Propose a structure for a compound with the formula C5H10O2 and the following spectra. ir Propose a structure for a compound with the formula C5H10O2 and the following spectra or draw as much structural information as you can about the unknown. ir nmr nmr integrations 3H 2H 2H 3H integrations 3 2 2 3 Propose a structure for a compound with the formula C5H10O2 and the following spectra. Does the compound contain a ring? A. yes B. no ir ΞC-H-C-H =C-H O-H N-H CO2H CΞN 3000 Propose a structure for a compound with the formula C5H10O2 and the following spectra. Does the compound contain an –OH group? A. yes B. no ir CΞC C=C C=O 1742 cm-1 1500 1000 600 ΞC-H-C-H =C-H O-H N-H CO2H CΞC C=C C=O 1742 cm-1 1500 1000 600 CΞN nmr 4000 2000 cm-1 nmr 4000 3000 2000 cm-1 integrations 3 2 2 3 integrations 3 2 2 3 Propose a structure for a compound with the formula C5H10O2 and the following spectra. Which nmr absorption represents a –OCH3 group? ir 1. no –OH 2. C=O 3. no rings nmr 4000 Propose a structure for a compound with the formula C5H10O2 and the following spectra. ir ΞC-H-C-H =C-H O-H N-H 3000 CΞC C=C C=O 1742 cm-1 1500 1000 600 1. no –OH 2. C=O 3. no rings nmr 4000 ΞC-H-C-H =C-H O-H N-H 3000 CΞC C=C C=O 1742 cm-1 1500 1000 600 CO2H CΞN CO2H CΞN 2000 cm-1 2000 cm-1 A integrations 3 B 2 C 2 D 3 3 O C CH 2 2 3 1 11/12/2010 Propose a structure for a compound with the formula C5H10O2 and the following spectra. Which partial structure is best represented by the multiplet at about 2.25 PPM? HH ir A CHCCR 1. no –OH 2. C=O 3. no rings nmr B H H R H C H H C H R Propose a structure for a compound with the formula C5H10O2 and the following spectra. ir 1. no –OH 2. C=O 3. no rings nmr H H H O O C H C H C H O C H H H D C H 2.25 PPM 6 lines? 2 3 2 2 3 3 2 3 Propose a structure for a compound with the formula C5H10O2 and the following spectra. ir 1. no –OH 2. C=O 3. no rings nmr A B How many absorptions would be predicted for the following hydrogens? A. 1 B. 2 C. 3 D. 4 E. 5 F. 6 3 2 6 lines? 2 3 3 Predict the nmr spectrum of the following compound. The methyl group (D) is responsible for the absorption at 1.88. A. true B. false (A) (D) (C) (B) chemical shift of methyl group absorptions 3.67 1.88 3 8 7 6 5 4 PPM 3 2 1 0 2 11/12/2010 HA is more deshielded than HB because of the inductive effect of the two oxygen atoms. A. true B. false Why is HA is more deshielded than HB because of resonance effects? H H3C H O O CH3 H3C H O O H CH3 Electronegativities: O = 3.5, C = 2.5, H = 2.1 (A) (D) (C) (B) (A) chemical shift of all absorptions HD = 3.67 HC = 1.88 (B) chemical shift of all absorptions HD = 3.67 HA = 6.90 HB = 5.76 HC = 1.88 HA = 6.90 8 7 6 HB = 5.76 5 4 PPM 3 2 1 0 8 7 6 5 4 PPM 3 2 1 0 How many lines would be predicted for hydrogens (C)? A. 2 B. 3 (A) (D) (C) (B) C. 6 D. 7 E. 8 F. 10 How many absorptions would be predicted for hydrogen (A)? A. 2 B. 3 (A) (D) (C) (B) C. 6 D. 7 E. 8 F. 10 HD HA 8 7 6 HC HB 5 4 PPM 4 3 2 1 0 8 7 6 8 7 6 5 PPM (δ) 3 2 1 0 8 HA 7 6 HB 5 5 4 PPM 4 PPM (δ) HD 3 3 2 2 HC 1 1 0 0 Why are there 8 absorptions for hydrogen (A)? Jac a c c How many Hz separate the two absorptions of Hc? A. 10 Hz a c c c b A. Because there are 4 adjacent hydrogens. B. Because the spin-spin coupling constants to HC and HB are unequal. b B. 6.85 Hz C. 15.5 Hz Jab c C. Because there are 8 hydrogens in this structure. Ha Ha Jab = 15.5 Hz Jac = 6.85 Hz 8 7 6 Jab = 15.5 Hz Jbc = 6.85 Hz 5 4 PPM 4 8 HA 7 6 HB 5 PPM (δ) HD 3 3 2 2 HC 1 1 0 0 8 8 7 HA 7 6 6 HB 5 5 4 PPM 4 PPM (δ) HD 3 3 2 2 HC 1 1 0 0 3 11/12/2010 How many absorptions would have been observed if Jab = Jbc? Jab Are there structures where coupling constants to non equivalent hydrogens are equal? Jab Jac Jac Ha Ha Jab = 15.5 Hz Jac = 6.85 Hz 8 7 6 Jab = 15.5 Hz Jac = 6.85 Hz 5 4 PPM 4 8 HA 7 6 HB 5 PPM (δ) HD 3 3 2 2 HC 1 1 0 0 8 8 7 HA 7 6 6 HB 5 5 4 PPM 4 PPM (δ) HD 3 3 2 2 HC 1 1 0 0 Other than hydrogen, do other nuclei have nmr absorptions? 13 1 HO HO O Both Both C and H have magnetic moments and can give nuclear magnetic resonance absorptions. Natural abundance of 13C 12C = 1% N O OH OH O O O O O OH O Most carbon, 99%, is O O In a 10 g sample, about how many grams contain at least one 13C atom? A. 0.01 g C. 1.0 g B. 0.1 g D. 5 g 25 rapamycin C51H79NO13 4 ...
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