2.7 - infrared spectroscopy

Define ground state

molecular vibration in the lowest possible energy state

Define wavenumber

reciprocal of wavelength and measured in cm^-1

What makes bonds vibrate?

all molecules absorb infrared radiation and absorbed energy makes bonds vibrate with stretching or bending motion

What makes it so different wavelengths can be displayed on an IR spectrum?

every type of bond vibrates at specific wavelength

What will most bonds vibrate between?

300 and 4000cm^-1

What is detected in an infrared spectrum?

energy not absorbed displayed as percentage transmittance

What is unusual about the IR spectrum?

scale decreasing

What is the region below 1300cm^-1 referred to as?

fingerprint region as pattern obtained characteristic of particular compound

How to identify functional group present?

analysis of IR spectrum identifies functional group present/homologous series compound belongs to, then exact compound identified from fingerprint region

What technique allows you to identify impurities in a sample using IR spectrum?

impurities displayed as addition peaks not present in spectrum of pure sample

What else can IR spectroscopy be used to do?

progress of chemical reaction as peak of functional group in reactant diminishes and peak for functional group in product appears