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Flashcards in organic analysis Deck (24)
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1
Q

what is the chemical test for alkenes

A

bromine water

orange>colourless

2
Q

chemical test for primary and secondary alcohols

A

acidified potassium dichromate and warm

3
Q

observation from chemical test with primary and secondary alcohols

A

orange>green

4
Q

observation from chemical test with tertiary alcohols

A

no colour change (tertiary alcohols cant be oxidised)

5
Q

chemical tests for aldehydes

A

tollens reagent- silver mirror

fehlings solution- blue solution>brick red ppt

6
Q

chemical test for carboxylic acids

A

sodium carbonate/hydrogencarbonate

effervescence

7
Q

chemical test for halogenoalkanes

A
silver nitrate solution and warm
hydrolysis and test for halide
cl- white ppt
br- cream ppt
I- yellow ppt
8
Q

what is infra-red spectroscopy

A

an analytical technique used to identify types of organic compounds

9
Q

what is ir spectrospcopy used to detect

A

the presence of specific covalent bonds within a compound

10
Q

how does ir spectroscopy detect the presence of specific covalent bonds within a compound

A

each type of bond vibrates at a specific frequency and so it absorbs a specific frequency of ir radiation

11
Q

what is an infra red spectrum

A

is a graph of % transmittance against wave number

12
Q

what is wave number proportional to

A

frequency

13
Q

what does the position of each inverted peak on ir spectrum tell us

A

which bonds are present and therefore which functional groups are present in organic compounds

14
Q

for which bonds are there two different absorptions

A

O-H (acids and alcohols)

15
Q

what is the fingerprint region

A

from about 500-1500cm-1

complex pattern of absorptions unique for each individual compound

16
Q

how can a compounds fingerprint region be identified

A

by comparing its finger region on a computer database

17
Q

examples of greenhouse gases

A

carbon dioxide
methane
water vapour

18
Q

why do greenhouse gases absorb infrared radiation

A

their bonds absorb infrared which makes it vibrate

19
Q

why do infrared spectra of greenhouse gases show big absorptions

A

bonds are efficient at absorbing infrared radiation

20
Q

why do the results contain many lines when an organic compound passes through a mass spectrometer

A
  • the fragment ions of the molecule

- molecule bombarded with highn energy electrons and so breaks apart

21
Q

molecular ion peak

A

the line with the largest m/z ratio in a mass spec. this peak gives mr of compound

22
Q

what can high resolution mass spec measure

A

the atomic and molecular mass to 4 dp

23
Q

what is high resolution mass spec useful for

A

when compounds have the same mr when rounded to the nearest whole number

24
Q

how can combustion analysis be used to determine the empirical formula of a compound

A

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