Section 4 Organic Analysis Flashcards
Describe the observations you would make:
1) Add 10 drops of primary alcohol to 2cm3 of acidified potassium dichromate solution in a test tube.
2) Warm the mixture gently in a hot water bath
Orange solution becomes green as aldehyde is formed.
Describe the observations you would make:
1) Add 10 drops of secondary alcohol to 2cm3 of acidified potassium dichromate solution in a test tube.
2) Warm the mixture gently in a hot water bath
Orange solution turns green as a ketone forms
Describe the observations you would make:
1) Add 10 drops of tertiary alcohol to 2cm3 of acidified potassium dichromate solution in a test tube.
2) Warm the mixture gently in a hot water bath
Nothing
Describe the observation you would make if you:
1) Put 2cm3 of Fehlings or Benedicts into a test tube.
2) Add 5 drops of aldehyde
3) Put the test tube in a hot water bath
Blue solution becomes a brick red precipitate
Describe the observation you would make if you:
1) Put 2cm3 of Fehlings or Benedicts into a test tube.
2) Add 5 drops of ketone
3) Put the test tube in a hot water bath
No change
How do you prepare Tollen’s reagent?
1) Put 2 cm3 of 0.1 moldm-3 silver nitrate in a test tube
2) Add a few drops of dilute sodium hydroxide solution - should see a light brown ppt
3) Add drops of dilute ammonia solution until the brown ppt dissolves completely
Describe the observation you would make if you:
1) Place the test tube of Tollen’s into a hot water bath
2) Add 10 drops of aldehydes
A silver mirror
Describe the observation you would make if you:
1) Place the test tube of Tollen’s into a hot water bath
2) Add 10 drops of ketone
Nothing
Describe the observation you would make if you:
1) Add 2cm3 of an alkene to a test tube
2) Add 2cm3 of bromine water
3) Shake
The solution will decolourise from orange to colourless.
Describe the observation you would make if you:
1) Add 2cm3 of carboxylic acid to a test tube
2) Add 1 small spatula of solid sodium carbonate
3) Bubble released gas through some limewater in a second test tube
The solution will fizz and the limewater will turn cloudy.
What is mass spectroscopy used for?
To determine the molecular formula of a compound
Describe the process of infrared spectroscopy?
A beam of IR radiation is passed through a sample of a chemical.
The IR radiation is absorbed by the covalent bonds in the molecules, increasing their vibrational energy.
Bonds between different atoms and bonds in different places in a molecule absorb different amounts of IR radiation
How is wavenumber calculated?
1/wavelength(cm)
What is the fingerprint region in infrared spectroscopy?
500-1500cm-1 - the section of an IR spectrum that is unique to a particular compound.
What is the greenhouse effect?
The sun emits electromagnetic radiation to earth
The earth re-emits some IR back
Molecules of greenhouse gases absorb this
These molecules reflect some back
etc
