Organic analysis 3.3.6

Question 1

what is the test tube reaction for an alkene?

Answer 1

Reagent = shake with bromine water
Result = Orange to colourless

Question 2

What are the two test tube reactions for an aldehyde ?

Answer 2

Reagent = fehlings solution
Result = blue solution to red ppt

Reagent = Tollens’ reagent
Result = Silver mirror formed

Question 3

What is the test tube reaction for a carboxylic acid?

Answer 3

Reagent = Sodium carbonate
Result = Effervescence of CO2 evolved

Question 4

What is the test tube reaction for primary and secondary alcohol and aldehyde ?

Answer 4

Reagent = acidified sodium dichromate and sulfuric acid
Result = Orange to green colour change

Question 5

What is the mechanism for the greenhouse effect?

Answer 5

• UV wavelength radiation passed through the atmosphere to earths surface and heats it up.
• Earth radiates out infrared long wavelengths radiation
• The C=O bonds in CO2 absorb IR so it doesn’t escape from the atmosphere.
• The energy is transferred to other molecules in the atmosphere by collisions so atmosphere is warmed

Question 6

What is the M peak?

Answer 6

The MR of the molecular ion

Question 7

what is the reagent used to identify between an alkene and a carboxylic acid and the observations?

Answer 7

hydrogencarbonate
Alkene = no visible change
Carboxylic acid = effervescence

Question 8

What is the test tube test for a halogenoalkane

Answer 8

1) add sodium hydroxide and warm
2) acidify with nitric acid
3) add silver nitrate

Result = precipitate of AgX(halogen)

Question 9

EQ : Give one reason why bonds in molecules such as carbon dioxide and 1,1,1 - trifluoroethane absorb infrared radiation (1)

Answer 9

Bonds are polar