organic analysis Flashcards
what is the chemical test for alkenes
bromine water
orange>colourless
chemical test for primary and secondary alcohols
acidified potassium dichromate and warm
observation from chemical test with primary and secondary alcohols
orange>green
observation from chemical test with tertiary alcohols
no colour change (tertiary alcohols cant be oxidised)
chemical tests for aldehydes
tollens reagent- silver mirror
fehlings solution- blue solution>brick red ppt
chemical test for carboxylic acids
sodium carbonate/hydrogencarbonate
effervescence
chemical test for halogenoalkanes
silver nitrate solution and warm hydrolysis and test for halide cl- white ppt br- cream ppt I- yellow ppt
what is infra-red spectroscopy
an analytical technique used to identify types of organic compounds
what is ir spectrospcopy used to detect
the presence of specific covalent bonds within a compound
how does ir spectroscopy detect the presence of specific covalent bonds within a compound
each type of bond vibrates at a specific frequency and so it absorbs a specific frequency of ir radiation
what is an infra red spectrum
is a graph of % transmittance against wave number
what is wave number proportional to
frequency
what does the position of each inverted peak on ir spectrum tell us
which bonds are present and therefore which functional groups are present in organic compounds
for which bonds are there two different absorptions
O-H (acids and alcohols)
what is the fingerprint region
from about 500-1500cm-1
complex pattern of absorptions unique for each individual compound
how can a compounds fingerprint region be identified
by comparing its finger region on a computer database
examples of greenhouse gases
carbon dioxide
methane
water vapour
why do greenhouse gases absorb infrared radiation
their bonds absorb infrared which makes it vibrate
why do infrared spectra of greenhouse gases show big absorptions
bonds are efficient at absorbing infrared radiation
why do the results contain many lines when an organic compound passes through a mass spectrometer
- the fragment ions of the molecule
- molecule bombarded with highn energy electrons and so breaks apart
molecular ion peak
the line with the largest m/z ratio in a mass spec. this peak gives mr of compound
what can high resolution mass spec measure
the atomic and molecular mass to 4 dp
what is high resolution mass spec useful for
when compounds have the same mr when rounded to the nearest whole number
how can combustion analysis be used to determine the empirical formula of a compound
react the organic compound in a large excess of oxygen and collect the products
mr of the compound can be determined from mass spectrum and hence empirical formula
