.6 Organic Analysis Flashcards
Tests to identify functional groups: alcohols, haloalkanes, alkenes, aldehydes, ketones, carboxylic acids (general- test and result)
Alkene (-C=C-): shake with bromine water
Result: orange colour disappears
Haloalkane (-R-X): 1. add NaOH(aq) and warm
2. acidify with HN03
3. add AgNO3(aq)
Result: precipitate of AgX
Alcohol (R-OH): add acidified K2Cr2O7
Result: orange colour turns green with primary or secondary alcohols (also with aldehydes) (do further test to see if ketone or aldehyde made by distilling- ketone= 2y aldehyde= 1y
Aldehydes (R-CHO)(At hind/END of chain): warm with Fehling’s solution
or
warm with Tollens’ solution
Result: F- blue colour turns to red precipitate
T- silver mirror forms
Carboxylic acids (R-COOH): add NaHC03 (aq) Result: CO2 given off- brisk effervesence
Testing for funct: group- alcohols, all steps, what oxidising agent, distinguishes between what, what colour change
1) Potassium dichromate to distinguish between primary, secondary and tertiary
2) If green, 2y/1y present
3) Fract dist for products- 1y= aldehyde 2y=ketone
4) Test to distinguish aldehydes/ketones (Tollen + Fehling)
5) If aldehyde formed, initial compound was PRIMARY
If ketone formed, initial compound was SECONDARY
Testing for funct group: Aldehydes from Ketones
warm with Tollen’s: silver mirror
warm with Fehling: blue to red precipitate
Testing for functional groups: Carboxylic acids- equation for one of tests
Turns blue litmus paper to red
OR
Add NaHCO3- releases CO2 (bubble through limewater)
What does mass spectometry do? What are its uses?
Identifies the chemical composition of a sample based on mass to charge ratio
detecting banned drugs
detecting toxins in food
locate oil deposits by testing rock samples
determine the extent of damage to human genes due to the environment
identify the country of origin of diamonds
Difference between mass spectrometry of compound vs element
Element: several lines- can use thes m/z ratios w/ relative abundance to work out Mr
Compounds: also several lines- one at the furthest right (the last peak) is actual Mr- mass of orginal molceule- molecule that hasn’t been fragmented (only lost one electron bc of electrospray)
With an element, each line represents a different isotope of that element. With a compound, each line represents a different fragment produced when the molecular ion breaks up
How to tell (from mass spectra) if a compound contains chlorine or bromine atoms? (and how many)
ONE CHLORINE: 2 peaks in molec ion region, sep by 2 m/z, 3:1 height ratio
Molecular ion peaks- 2
Why? Two isotopes- 35Cl 37Cl ratio 3:1
Ratio? 3:1
TWO CHLORINES: 3 peaks in molec ion region, sep by 2 m/z each, 9:6:1 height
Molecular ion peaks- 3
Why? (table below)
Ratio? 9:6:1
BROMINE: 2 peaks in molec ion region, sep by 2 m/z, nearly same height
Molecular ion peaks- 2
Why? Two isotopes- 79Br 81Br
Ratio? 1:1
What is a problem with mass spectrometry? How can it be solved?
Not extremely accurate masses- rounded to whole number
High resolution mass spectometry- identifies different molecules with the same molecular mass rounded to the nearest whole number
What happens in an infra-red spectrometer?
This is what happens in an infrared spectrometer:
1 A beam of infrared radiation containing a spread of frequencies is
passed through a sample.
2 The radiation that emerges is missing the frequencies that
correspond to the types of bonds found in the sample.
3 The instrument plots a graph of the intensity of the radiation
emerging from the sample, called the transmittance, against the
frequency of radiation.
4 The frequency is expressed as a wavenumber, measured in cm- 1
What can the fingerprint region be used for?
Unique to every compound
-Identify compound: compare to spectra of known compond
Check purity: compare to spectra of pure compound. If has more peaks, due to impurities.
what are spec. rules to help distinguish IR spectra
C-H: ALWAYS around 300 but
saturated- below 3000 unsaturated- above 3000 aldehydes- below 2730
O-H: very broad, alcohols higher than carb acids
C=O: ald, ket, car, est- all 1700
C=C: alkenes- small peak- 1650
IR absorption and Global Warming- what do GGs do, what are some examples of them, what does absorption of IR do to these molecules, what has increased global warming
-Uv/visible radiation emitted by the sun is adsorbed by the Earth’s surface and re-emitted as IR radiation.
CO2, Water and Methane molecules (greenhouse gases) in the earth’s atmosphere absorb this IR causing the bonds to vibrate.
The more IR that is absorbed leads to more global warming.
Human activity e.g burning fossil fuels, landfills (methane from decomposition)
