chapter 16 - organic analysis Flashcards
functional group tests for alkenes (C=C)
test with bromine water. (Br2)aq
orange solution to colourless solution.
CH2=CH2 + Br2 = CH2BrCH2Br
Functional group tests for halo alkanes
Hydrolyse then add NaOH, then HNO3, then AgNO3
C-Cl = Silver chloride produces a white precipitate
C-Br = Silver bromide produces a cream precipitate
C-I = Silver iodide produces a yellow precipitate
Functional group tests for a tertiary alcohol
Add acidified potassium dichromate, (heat with dilute sulphuric acid)
The orange solution will remain orange as no reaction occurs. There is no visible change
Functional group tests for a secondary and primary alcohol
Add acidified potassium dichromate, (heat with dilute sulphuric acid)
The orange solution will turn to a green solution
Functional group tests for an aldehyde
Fehlings solution - fehlings A and fehlings B (heated gently)
A blue solution turns to a brick red precipitate
Tollens reagent - Silver nitrate (AgNO3 & ammonia NH3)
A colourless solution will turn to a silver mirror
Functional group tests for a carboxylic acid
These compounds react with sodium carbonate producing carbon dioxide gas this gas can be collected and tested using lime water and the solution will be cloudy if the gas is carbon dioxide.
What is a fingerprint region
A fingerprint region is to the right hand side of the IR spectrum. This contains tiny differences from species to species which act as a molecules fingerprint. Allowing it to be identified
Tell me about global warming and infrared spectrums
Infrared absorption also occurs in the atmosphere with molecules such as ozone. This causes heat to be trapped within the earths atmosphere, this is an important factor for the existence of life. However when chemicals such as chlorofluorocarbons are released into the atmosphere from human activity this heating is enhanced leading to global warming
Describe mass spectrometry
It is an analytical technique used to identify compounds and determine the molecular formula.
High resolution my spectrometry
Is a more sensitive form of mass spectrometry which allows the Mr of a substance to be determined to several decimal places. Precise atomic masses are always given and can then be used to calculate the molecular formula of the compound being tested.
Describe infrared spectroscopy
It is an analytical technique which uses infrared radiation to determine the functional groups present in organic compounds. The IR radiation is passed through a sample where the different types of bonds absorb the radiation in different amounts. These varying amounts of absorbance are measured and recorded allowing certain bonds therefore functional groups to be identified.
A spectrum is produced from the measurements which has a characteristic curve for the different functional groups
What is meant by the term greenhouse gas
Greenhouse gases absorb/reflect infrared radiation from the earth
Greenhouse gases and
global warming
Only gases that contain polar bonds can absorb infrared radiation. [Even a non-polar symmetrical molecule]
Absorption of infrared radiation results in bonds undergoing stretching or bending
Examples of greenhouse gases all: carbon dioxide, ozone, water vapor, nitrogen monoxide, methane.
1) Solar radiation passes through the earths atmosphere [ultraviolet and visible light]
2) Radiation is absorbed by earths surface. And the earth emmits infrared radiation.
3) Some heat is absorbed by bonds/gases in the atmosphere
