3.6 Organic analysis

Question 1

What is the test for alkenes?

Answer 1

Bromine water
Orange to colourless

Question 2

What is the test for haloalkanes?

Answer 2

1. Add aqueous NaOH
2. Acidify with HNO3
3. Add AgNO3
4. Add dilute ammonia
5. Add conc ammonia

A white cream or yellow precipitate will form if Cl, Br or I is present
AgCl will dissolve in dilute ammonia
AgBr will dissolve in conc ammonia

Question 3

What is the test for 1 or 2 degree alcohols?

Answer 3

Add acidified K2Cr2O7
Heat

Solution will turn orange to green

Question 4

What is the test for aldehydes?

Answer 4

Warm with feihlings or tollens solution

F - Blue solution turns to brick red ppt
T- Silver mirror forms

Question 5

What is the test for a carboxylic acid?

Answer 5

Add Na2CO3

Effervescence as CO2 given off

Question 6

What is the test for H2 gas?

Answer 6

Lit splint

A squeaky pop

Question 7

What is the test for CO2 gas?

Answer 7

Bubble through lime water

Will turn cloudy

Question 8

What is the test for O2 gas?

Answer 8

Apply a glowing splint

Splint will relight

Question 9

What is the test for sulphate ions?

Answer 9

Add BaCl2 solution

A white precipitate will form

Question 10

What is the test for halide ions?

Answer 10

Add HNO3 then AgNO3

Cl - white ppt
Br - cream ppt
I - yellow ppt

Question 11

What is the test for CO3 2- ions?

Answer 11

Add any acid

Effervescence

Question 12

What is infrared spectroscopy used to identify?

Answer 12

The functional group of an organic molecule

Question 13

What kind of frequency do strong bonds have?

Answer 13

High frequency

Question 14

What kind of frequency do weak bonds have?

Answer 14

Low frequency

Question 15

How does infrared spectroscopy work?

Answer 15

Infrared energy is absorbed by bonds which makes bonds vibrate
The bonds vibrate at the same frequency as the infrared energy

Question 16

Describe the process which happens in an IR spectrometer

Answer 16

1. A beam of IR light is passed through a sample
2. Some of the frequencies of the IR are absorbed, many are not absorbed so pass through
3. The light that emerges on the other side is missing the frequencies that were absorbed
4. A computer then plots a graph called transmittance

Question 17

What are the peaks on a spectra graph called?

Answer 17

Absorptions

Question 18

What does the absorption of a O-H (alcohol) bond look like?

Answer 18

Broad
Smooth
Mitten shaped

Question 19

What does the absorption of a O-H (carboxylic acid) bond look like?

Answer 19

Broad
Jagged
Glove shaped

Question 20

How does global warming occur?

Answer 20

The OH bonds in water, C=O bonds in CO2 and C-H bonds in methane absorb infrared radiation
The IR emitted by the earth is trapped and not allowed to escape into the atmosphere

Question 21

What is the fingerprint region?

Answer 21

The area of the spectrum below 1500 cm-3

Question 22

How can IR spectroscopy be used to confirm that a compound is definitely ethyl butanone?

Answer 22

Compare the fingerprint region to a known spectrum from a database, it should be an exact match

Question 23

What is the peak with the largest m/z value called?

Answer 23

Molecular ion peak

Question 24

What can you find from the molecular ion peak?

Answer 24

The m/z value

Question 25

Why does carbon have a relative moleccular mass of 12?

Answer 25

12C is the standard reference