09-20 - What infrared absorption would be predicted for the...

Info icon This preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 9/21/2010 What infrared absorption would be predicted for the C=O group of 2-butenone? A. 1686 cm-1 B. 1728 cm-1 2-butenone C=O = ???? cm-1 Molecules have many different vibrational possibilities. butanone C=O = 1710 cm-1 O O How do the resonance structures of these two compounds differ? O 1 2 How many vibrational modes are possible? 3n-6 = number of vibrational modes n = number of atoms in a molecule How many vibrational modes would be predicted for formaldehyde (CH2=O)? A. 3 B. 6 C. 8 D. 20 E. 32 F. >32 3n-6 = number of vibrational modes 3n-6 = 3(4) – 6 = 6 3 4 Any molecule has 3n-6 vibrational modes where n = number of atoms present in the molecule. How many vibrational modes would be predicted for ibuprofen? OH 1750 cm-1 1165 cm-1 C13H18O2 O ibuprofen = 3n – 6 = 3(33) – 6 = 93 vibrational modes A. 3 B. 6 C. 8 D. 20 E. 32 F. >32 6 1 9/21/2010 Which functional group in ibuprofen is responsible for the strong absorption at 1721 cm-1? ΞC-H C-H =C-H O-H CO2H CΞC C=C C=O N-H CΞN 3000 A. C-H C- B. C=O C. C=C D. O-H O- E. C-C C- 4000 A. C-H B. C=O 2000 C. C=C cm-1 1500 D. O-H 1000 E. C-C 600 OH O O OH * 7 * 8 Why is the C=O bond stretch the most intense? + = hν Why is the C=O bond stretch the most intense? + hν = hν v=0 v=1 OH O O OH Why is the C=O bond stretch the most intense? + δ δ v=0 hν δ v=1 4000 = hν δ ΞC-H -C-H =C-H O-H CO2H CΞC C=C C=O orgchem web site N-H 3000 CΞN 2000 cm-1 1500 1000 600 A. A. The oxygen and carbon are the heaviest atoms. B. This vibration represents the largest change in dipole moment. C. The C=O bond is the strongest. O OH 2 9/21/2010 13 14 Do all C-H bonds have the same strength? CCΞC C-H p -C-H =C-H ΞC-H s energy C=C high energy 4000 3000 2000 cm-1 1500 1000 low energy 600 Which of the following has the C-H bonds correctly assigned to the above infrared absorptions: , and ? A. C. E. ΞC-H -C-H =C-H =C-H ΞC-H -C-H -C-H =C-H ΞC-H B. D. F. ΞC-H -C-H =C-H -C-H =C-H ΞC-H =C-H ΞC-H -C-H Csp—H1s A. Csp2—H1s Csp3—H1s ΞC-H =C-H -C-H increasing strength of the C-H bond C- CΞC C-H C=C ΞC-H -C-H =C-H O-H CO2H CΞC C=C C=O N-H 4000 3000 2000 cm-1 1500 1000 600 4000 3000 CΞN 2000 cm-1 1500 1000 600 Which of the following has the C-H bonds correctly assigned to the above infrared absorptions: , and ? A. C. E. ΞC-H -C-H =C-H =C-H ΞC-H -C-H -C-H =C-H ΞC-H B. D. F. ΞC-H -C-H =C-H -C-H =C-H ΞC-H =C-H ΞC-H -C-H A. ΞC-H =C-H -C-H 3 9/21/2010 ΞC-H -C-H =C-H O-H (s) CO2H CΞC C=C ΞC-H -C-H =C-H CΞC C=C C=O(s) N-H 4000 3000 CΞN 2000 cm-1 Which structure is consistent with the following ir spectrum? 1000 600 4000 O-H CO2H C=O N-H 3000 O OH O OH CH3 CΞN 2000 cm-1 Which structure is consistent with the following ir spectrum? 1500 1000 600 1500 C=O overtone ? ? O OCH3 O O OH A OCH3 O D OH O OH OH OH O A B C D B OCH3 C OCH3 ΞC-H -C-H =C-H O-H CO2H CΞC C=C ΞC-H -C-H =C-H CΞC C=C C=O N-H 4000 3000 CΞN 2000 O CH3 O O OH Which structure is consistent with the ir spectrum? 1500 1000 600 4000 O-H CO2H C=O N-H 3000 CΞN 2000 cm-1 Which structure is consistent with the ir spectrum? 1500 1000 600 cm-1 OH O OH CH3 O O O OH OH O OH D OH O A OCH3 O OCH3 O OCH3 A OH OCH3 O OCH3 D B C OCH3 B C Why Communicating Science Matters: A conversation between Alan Alda and Brian Greene Thursday, September 23, 2010 4:00pm to 5:00pm Staller Center Auditorium- Free and open to the public 4...
View Full Document

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern