Unit 3: Section 4- Organic Analysis + RP6 Flashcards
What can a mass spectrum show?
the whole molecule and fragments of a molecule
Define molecular ion
the molecule with one electron
knocked off (It is both an ion and a free radical)
What can high resolution mass spectrometers be used to determine?
the molecular formula of a compound
they can help differentiate between compounds that appear to have similar Mr
How many peaks on a mass spectroscopy will chlorine and bromine produce and why?
2 because they have 2 naturally occurring isotopes
What importance does 1500cm-1 have in infrared spectrscopy?
above- functional group identification
below- ‘fingerprinting’
Describe the fingerprinting region of infrared spectroscopy
complicated
unique for every compound
Why can infrared spectroscopies identify molecules?
because certain groups in a molecule absorb infra-red radiation at characteristic frequencies
What can infrared spectroscopies be used for?
they can identify functional groups
they can identify impurities
fingerprinting
Describe O-H absorptions
tend to be broad
What can rouge absorptions indicate?
impurities
Describe the mechanism of the greenhouse effect
UV wavelength radiation passes through the atmosphere to the Earth’s surface and heats up Earth’s surface.
The Earth radiates out infrared long wavelength radiation.
The C=O Bonds in CO2
absorb infrared radiation so the IR radiation does not escape from the atmosphere.
This energy is transferred to other molecules in the atmosphere by collisions so the atmosphere is warmed.
RP 6- Describe the test and result for an alkene
Bromine water
orange solution decolourises
RP 6- Describe the test and result for an aldehyde with Fehling’s solution
Conditions: heat gently
Reaction: aldehydes only are oxidised by Fehling’s Solution
into a carboxylic acid. The copper (II) ions are reduced
to copper(I) oxide .
Observation: Aldehydes :Blue Cu 2+ ions in solution change to
a red precipitate of Cu2O. Ketones do not react
RP 6- Describe the test and result for an aldehyde with tollen’s reagent
Conditions: heat gently
Reaction: aldehydes only are oxidised by Tollens’ reagent into a carboxylic acid. The silver(I) ions are reduced to silver atoms
Observation: with aldehydes, a silver mirror forms coating the inside of the test tube. Ketones result in no change.
RP 6- Describe the test and result for a 1o 2o alcohol and aldehyde
sodium dichromate and sulphuric acid
orange to green colour change
RP 6- Describe the test and result for a chloroalkane
warm with silver nitrate
slow formation of white precipitate of AgCl
What is the purpose of mass spectrometry?
identify an unknown compound
What does mass spectrometry measure?
mass-to-charge ratio of ions
What is the definition of a molecular ion?
electrons are removed from an organic molecule to form a positive ion
What is the symbol for a molecular ion?
M+
What is the charge of a molecular ion?
positive
What is a feature of a molecular ion?
unstable
What type of radiation is used for infrared spectroscopy?
infrared radiation
What units are used during infrared spectroscopy?
cm-1
