Is lower than the c h stretching frequency 3000 cm 1

Info iconThis 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: 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 wavelengths? – 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 in vibrational by wavenumber H-X ( cm-1) HF > 565 19.0 0.95 HCl > HBr > HI 427 363 295 35.5 79.9 126.9 0.97 0.99 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 Stretches increases Energy increases C-H stretch 24 12 Question #1 Which molecule has the strongest C-C bond? Absorption Wavelength A....
View Full Document

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.

Ask a homework question - tutors are online