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Unformatted text preview: lower than the C-H stretching frequency
(3000 cm-1) . (reduced masses differ by ~2)
• So, what would that indicate about the relative
what would that indicate about the relative
– C-D would absorb at a longer wavelength than C-H. 22 11 Interpreting IR stretching frequencies
• HX molecules exhibit effects due mainly to decreasing bond
energy. (reduced mass changes very little for the HX series)
– Trend in vibrational frequency by wavenumber
by wavenumber H-X ( cm-1) HF >
0.95 HCl > HBr > HI
0.99 4138 Bond Energies
Atomic mass of X
Reduced mass of HX 2991 2650 2309* *Note that this means that HI absorbs at the largest wavelength. 23 C C, C=C, & C C
CH3CH2CH2CH2CH2CH3 C=C stretch =CH2 stretch C C stretch C-C Stretches &
H-C-H bends CH3CH2CH2CH2CH=CH2
CH3CH2CH2CH2C CH C-H Stretches
C-H stretch 24 12 Question #1
Which molecule has the strongest C-C bond?
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This note was uploaded on 01/24/2014 for the course CHEM 115 taught by Professor L during the Fall '02 term at Purdue University-West Lafayette.
- Fall '02