Organic analysis. Flashcards
How many bonds are broken during fragmenation.
One bond is broken and it is usually the C-C bond.
What is the highest fragmentation peak caused by.
The most stable species will cause this greatest peak - the carbocation.
Define the molocular ion and give the species that ethanol will form when it traveles through the mass spectromoeter.
In mass spectrometry the molecular ion is the molocule of the sample that has been ionised but has not broken up during its flight through the instrument.
If you are asked for a species or anything to do with what has actually travled through the instrument you MUST GIVE THE FORMULA OF AN ION.
For ethanol C2H5OH+ or structural will be {CH3CH2OH+}.
Definition: Molecular ion is the molocule with one electron knocked off, (it is both an ion and a free radical.)
In general:
Molecular ion formed: M → [M]+.+ e
What is detected when organic molocules are passed through a mass spectrometer.
When organic molecules are passed through a mass spectrometer, it detects both the whole molecule and fragments of the molecule.
Why in general would reflux conditions be used. (heating under reflux)
This would ensure that a reaction will go to completion. For example fully oxidised.
In the mass spectrometer which of the two parts of a fragment will be detected.
The fragment Ion [X+] will be detected wheres the corrasponding free radial will not be.
What needs to be known when you are testing organic compounds.
You need to establish the functional group that is present.
What does a solid compound suggest.
This suggests that there is a long carbon chain or possible ionic bonding for a hgher melting point. Note ionic bonding is much stronger than H- bonding that would be present in luiqids.
What does a luiqid suggest about the nature of a compound.
It suggests that there is a medium length carbon chain or possibly hydrogen bonding or polarity present.
What does a gaseous compoud tell you about its nature.
It tells you that it has a short carbon chain or little to no polarity.
What does it suggest if a compound does disolve in water.
This suggests that there is polar groups if it does disolve in water or that there isnt polar groups if it doesnt disolve in water.
What does it suggest if a compound is acidic.
This suggests that the compound is a carboxylic acid.
Give the test tube reaction for an alkene functional group and the result if the test is possitive.
Shake with bromine water. The orange colour of the bromine will disapeare as (electrophilic addition occurs)
Give the test tube test for the reaction of an alcohol functional group, R-OH. Give the observation if the test is possitive.
What specific alcoholes does this work for and one other functional group.
Add acidified K2Cr2O7 . The orange colour will turn will turn green (think same starting colour as with bromine) , and this will be the case for both primary and seconadry alcoholes in addition to aldehydes.
Give a simple chemical test for an aldehyde functional group , R-CHO. State the observation if the test is possitive.
Warm with fehlings solution for colour change from blue to brick red precipitate.
Or use Tollens solution to get a silver mirror form.
Give a simple chemical test for a carboxylic acid functional group, R-COOH. Give the observation if the test is possitive.
Add aqeous NaHCO3 to see effervescence of carbon dioxide evolved.
Give a simple test to identify a holoalkane, R-X, and then also the test that would be done to specifically identify a chloroalkane , R-Cl .
Add NaOH Acidify with HNO3 Add AgNO3 and warm Precipitate of AgX will form. Warming with silver nitrate would cause the slow formation of a white precipitate of AgCl.
What can high resolution mass spactrometry be used for and why would it be needed to be done. Refer to how high resolution mass spectrometry is any different to normal spectrometry in your answer.
High resolution mass spectrometry can be used to determine the molecular formula of a compound from the accurate mass of the molecular ion.
High resolution mass spectroscopy can measure the mass to 5d.p. This can help differentiate between compounds that appear to have similar Mr (to the nearest whole number).
Forexample, the following molecular formulas all have a rough Mr of 60, but a more precise Mr can give the molecular formula. e.g
.Mr=60.02112 molecularformula=C2H4O2
Mr=60.05751 molecular formula=C3H8O
Mr=60.03235 molecular formula=CH4N2O
A compound is found to have an accurate relative formula mass of 46.0417. It is thought to be either CH3CH2OH or H2NCH2NH2. Calculate the Mr of each compound to 4 decimal places to work out which one it is.
Given Accurate masses of atoms:
H = 1.0078 C = 12.0000 O = 15.9949 N = 14.0031
Working and answer: CH3CH2OH = (12.0000 x 2) + (15.9949 x 1) + (1.0078 x6) = 46.0417
H2NCH2NH2. = (12.0000 x 1) + (14.0031 x 2) + (1.0078 x6) = 46.0530
So it is CH3CH2OH
What is the mass number of carbon.
Carbon has a value of 12.0000, as it is by definintion the standard reference.
Give the two isotopes that chlorine and bromine can exist as and state the relative abundances of each.
Chlorine exists as Cl-35 (75%) and Cl-37(25%).
Bromine exists as Br-79( 50%) and Br-81 (50%).
If an organic compound contains either chlorine or bromine then what can you expect the mass spectrum for that organic compund to look like. Also refer to the name of the concept you are refering to in your answer.
If a compound contains a chlorine or a bromine atom then two molecular ion peaks will occur : an M peak and an M+2 peak will occur due tothe two naturally occurring isotopes of chlorine or bromine.
This concent is the M / M+2 idea.
Why can organic compounds containing both Cl and Br have their peaks considered in the same M and M+2 way even though the peaks will be in different ratios.
This is as both have two naturally occuring isomers with the same mass difference of 2. Cl-35 (75%) and Cl-37(25%). Br-79( 50%) and Br-81 (50%). Therefore even though the ratio of the peaks will differ due tothe difference in abundances the difference in mass will be the same between a compound containing one particular isomer and one that contains the other weather its Cl or Br.
Give the M/Z value of the molecular ion peak for CH3Cl in a mass specrum and state the ratio that the peaks will be in.
CH3Cl will have a m/z value of M of 50 CH3Cl 35 and M+2 of 52 CH3Cl 37 The ratio of heights M:M+2 will be 3:1.
