HW#7 - Smartwork Ch. 3 - Due 10/9 (Monday) @ 10 AM - more Smartwork coming soon.•Nomenclature 2 Memorization Quiz Monday @ class time (10/9)•Please respond to the Organic II Lab Survey by Sunday afternoon if you plan to take Organic II in •the spring. I'll be choosing the new lab section time on Sunday evening.There will be a Research Techniques section of Organic II lab in the spring - see the •announcement on Piazza for more information. See me or Dr. Goforth for an application (due 10/20)Mark your calendar for SNCURCS at Campbell on Saturday, Nov. 4th. NC Academy of Science •workshops also occurring. Abstract submissions (due 10/18) and registration at www.sncurcs.org Monday we'll begin Ch. 4•

Textbook Homework and Reading Assignment:

Reading: Finish reading Nomenclature 2 and read Ch. 4•Textbook problems: 15.4, 15.9, 15.28, 15.32, 15.34(a-c), N2.1, N2.2, N2.3, N2.4, N2.5, N2.6, •N2.7, N2.9, N2.10, N2.11, N2.12, N2.13, N2.14

All thestructuresto the rightAre alsotrans-2-bromobut-2-eneThey are just rotated or flippedover when compared to thestructure at the top

And power point slides, following the notes

Chapter 15: UV-Vis Spectroscopy

•  The number of MOs must be equal to the number of combined atomic orbitals (AOs).

•  Note how the shorthand drawing matches the actual MOs.

Molecular Orbital Theory

Copyright 2012 John Wiley & Sons, Inc.

Klein, Organic Chemistry 1e 17-2

•  1,3,5-hexatriene should have six pi MOs. –  What are

HOMO and LUMO?

•  The HOMO and LUMO are the frontier MOs.

Molecular Orbital Theory

Copyright 2012 John Wiley & Sons, Inc.

Klein, Organic Chemistry 1e 17-3

Conjugated Chain MO’s

Higher Frequency Higher Energy

Lower Frequency Lower Energy

Electromagnetic Radiation

E = hν

C = λ ν

Ultraviolet–visible spectroscopy (UV-vis)

•  UV-Visible (UV-Vis) spectroscopy gives structural information about molecules:

–  The resulting data is plotted to give a UV-Vis absorption spectrum.

–  Compounds require specific wavelengths of energy to excite. WHY?

UV-Vis Spectroscopy

Copyright 2012 John Wiley & Sons, Inc. Klein, Organic Chemistry 1e 17-7

Color of light complementary λ(nm) absorbed color

(color reflected)

< 400 UV 425 violet yellow 470 blue orange 520 green red 570 yellow violet 620 orange blue 680 red green

>700 IR

Color

•  The visible region of the spectrum (400-700 nm) is lower energy than UV radiation.

•  Lycopene is responsible for the red color of tomatoes.

•  β-carotene is responsible for the orange color of

carrots.

Color

Copyright 2012 John Wiley & Sons, Inc. Klein, Organic Chemistry 1e 17-9

•  Bleaching agents generally work by breaking up conjugation through an addition reaction.

•  Destroying long range conjugation destroys the ability to absorb colored light. WHY?

•  Does bleach actually remove stains?

Color

Copyright 2012 John Wiley & Sons, Inc. Klein, Organic Chemistry 1e 17-10