organic analysis

Question 1

what is the chemical test for alkenes

Answer 1

bromine water

orange>colourless

Question 2

chemical test for primary and secondary alcohols

Answer 2

acidified potassium dichromate and warm

Question 3

observation from chemical test with primary and secondary alcohols

Answer 3

orange>green

Question 4

observation from chemical test with tertiary alcohols

Answer 4

no colour change (tertiary alcohols cant be oxidised)

Question 5

chemical tests for aldehydes

Answer 5

tollens reagent- silver mirror

fehlings solution- blue solution>brick red ppt

Question 6

chemical test for carboxylic acids

Answer 6

sodium carbonate/hydrogencarbonate

effervescence

Question 7

chemical test for halogenoalkanes

Answer 7

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

Question 8

what is infra-red spectroscopy

Answer 8

an analytical technique used to identify types of organic compounds

Question 9

what is ir spectrospcopy used to detect

Answer 9

the presence of specific covalent bonds within a compound

Question 10

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

Answer 10

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

Question 11

what is an infra red spectrum

Answer 11

is a graph of % transmittance against wave number

Question 12

what is wave number proportional to

Answer 12

frequency

Question 13

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

Answer 13

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

Question 14

for which bonds are there two different absorptions

Answer 14

O-H (acids and alcohols)

Question 15

what is the fingerprint region

Answer 15

from about 500-1500cm-1

complex pattern of absorptions unique for each individual compound

Question 16

how can a compounds fingerprint region be identified

Answer 16

by comparing its finger region on a computer database

Question 17

examples of greenhouse gases

Answer 17

carbon dioxide
methane
water vapour

Question 18

why do greenhouse gases absorb infrared radiation

Answer 18

their bonds absorb infrared which makes it vibrate

Question 19

why do infrared spectra of greenhouse gases show big absorptions

Answer 19

bonds are efficient at absorbing infrared radiation

Question 20

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

Answer 20

• the fragment ions of the molecule

- molecule bombarded with highn energy electrons and so breaks apart

Question 21

molecular ion peak

Answer 21

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

Question 22

what can high resolution mass spec measure

Answer 22

the atomic and molecular mass to 4 dp

Question 23

what is high resolution mass spec useful for

Answer 23

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

Question 24

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

Answer 24

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