Chapter 17 - spectroscopy Flashcards
What is infrared spectroscopy used for?
To identify the presence or absence of bonds in a molecule - can give v useful information about whether a functional group is present in a molecule
How does infrared spectroscopy work?
A beam of IR radiation of a range of frequencies is passed through a sample. The bonds in the molecule absorb energy at different frequencies. The absorption of the infrared causes the covalent bonds to vibrate more as they absorb energy
What is the wavenumber and possible functional group of a C-H bond?
2850-3100 cm-1 Any organic compound with a C-H bond.
What does a C-H bond look like on a IR spectroscopy graph?
2 tongued sharp spikes
What is the wavenumber and possible functional group of a C=O bond?
1640-1750 Aldehydes, ketones, carboxylic acids
What does a C=O bond look like on an IR graph?
A sharp narrow spike
What is the wavenumber and possible functional group of an O-H bond and how can you differentiate between the two possible groups?
3200-3550 alcohols 2500-3300 carboxylic acids - very broad on graph
What does a carboxylic acid look like on an IR graph?
A very broad and bumpy section
What does an alcohol look like on an IR graph?
Wide and smooth section
What must you include in an answer about IR spectroscopy?
Reference waver number Reference functional group Reference what organic molecule it is
What are 2 uses of IR spectroscopy?
Modern breathalysers that measure ethanol in the breath bu analysis using IR spectroscopy To monitor gases causing air pollution
What is mass spectrometry used for?
To investigate the structure of organic molecules including the determination of Mr values
What happens when a molecule is passed through a spectrometer?
It will break down via a process called fragmentation
What does the peak furthest right show?
The Mr value of the molecule
List 4 common fragments
CH3+ CH2CH3+ CH2OH+ CH2CH2OH+
