FTIR Introduction

What is conditions of compounds to absorb IR radiation?

• Molecule must be symmetrical, polar and no dipole moment

• Molecule must be unsymmetrical, non-polar and no dipole moment

• Molecule must be symmetrical, polar and have a dipole moment

• Molecule must be unsymmetrical, polar and have dipole moment

What is the function of IR spectroscopy?

• Identify the functional groups

• electronic transition

• nuclear spin

• mass of atom

What are the units most commonly used to identify bands in FTIR spectroscopy?

• Wavenumbers(cm-1)

• Wavelength(m)

• Frequency(Hz)

• Wavelength(micrometres)

A particular bond absorbs in the IR, depends on

I- Atomic Size

II-Electronegativity

III- Bond strength

IV-Atomic mass

• I and III

• I and II

• III and IV

• II and IV

What is the predictable region for the C=C, C=O and C=N in the IR spectrum

• 4000-2500 cm-1

• 2000-1500 cm-1

• 2500-2000 cm-1

• 1500-400 cm-1

State the stretching frequencies of symmetrical and asymmetrical of C-H

• 1450 and 1350 cm-1

• 2853 and 2926 cm-1

• 2853 and 1450 cm-1

• 2926 and 2853 cm-1

For two atoms with the same weight on each end, the molecules vibrates at

• lower frequency

• higher frequency

• strong transmittance

• low transmittance

For two atoms with the same strength, the molecules with higher mass vibrates at

• lower frequency

• higher frequency

• strong transmittance

• low transmittance

What is the predictable region for the C-H, O-H and N-H in the IR spectrum

• 4000-2500 cm-1

• 2000-1500 cm-1

• 2500-2000 cm-1

• 1500-400 cm-1

What is the predictable region for the C-C, C-O, and C-N in the IR spectrum

• 4000-2500 cm-1

• 2000-1500 cm-1

• 2500-2000 cm-1

• 1500-400 cm-1