C16. Organic Analysis

Question 1

What is the test for an alcohol?

Answer 1

Acidified Potassium Dichromate (K2Cr2O7); Oxidises primary and secondary alcohols, not tertiary; Oxidising agent ,reduces itselfs; Orange to green

Question 2

What is the test for aldehydes and ketones?

Answer 2

Fehling’s solution; Oxidising agent, reduces itself; Oxidises aldehydes but not ketones; Add warm Fehling’s solution to aldehyde; Blue solution to brick red precipitate

Question 3

How do you create Tollens’ reagent?

Answer 3

Silver nitrate solution (colourless); Add drops of NaOH, pale brown precipitate forms; Add drops of dilute ammonia until precipitate dissolves; No reaction with ketones , stays blue

Question 4

How does Tollens’ reagent react with aldehydes and ketones?

Answer 4

Add aldehyde to Tollens’ reagent and warm in hot water bath; Silver precipitate forms; No reaction with ketones

Question 5

What is the test for alkenes?

Answer 5

Add bromine water to alkene and shake; orange to colourless; Bromine water reacts with double bond, dibromoalkane formed (colourless)

Question 6

What is the test for carboxylic acids?

Answer 6

React with carbonate (sodium carbonate) , forms CO2; CO2 bubbled through limewater turns cloudy

Question 7

What is mass spectroscopy used for?

Answer 7

Find relative molecular mass of a compound

Question 8

What is the molecular ion peak?

Answer 8

Last peak; shows relative molecular mass of molecule

Question 9

What does high resolution mass spectroscopy do?

Answer 9

Measures relative mass to several decimal points; Useful for identifying different molecules with same molecular mass rounded to nearest whole number

Question 10

How does Infrared (IR) Spectroscopy work?

Answer 10

Uses infrared radiation to increase vibrational energy of covalent bonds in a sample

Question 11

What factors affect frequency of covalent bonds in IR Spectroscopy?

Answer 11

Atoms on either side of bond; position of bond in molecule

Question 12

What is a fingerprint region of IR Spectrum?

Answer 12

Region between 500 cm-1 and 1500 cm-1; size and position of peaks are unique to a particular molecule; compare fingerprint regions against known library of spectra to identify molecule

Question 13

What are the greenhouse gases?

Answer 13

CO2, H2O, CH4

Question 14

What is the process of greenhouse effect?

Answer 14

Electromagnetic radiation from Sun reaches Earth; absorbed by land and sea, re-emitted as infrared radiation; greenhouse gasses absorb IR radiation into covalent bonds; re-emit IR radiation back to earth warming it

Question 15

What is increasing greenhouse gasses?

Answer 15

Human activities; burning fossil fuels; landfill

Question 16

What is global warming?

Answer 16

Gradual warming of the Earth; generally due to the greenhouse effect