What's in a Medicine - Unit 5 Flashcards
What is some alchohols solubility with water?
Missible (mixable) with water
What alcohols are not missible with water and why?
1 - Ocatn-1-ol (long chain alcohols)
2 - Because lot’s of hydrogen bonds need breaking in the water
Describe the oxidation of a primary alcohol to carboxylic acid? (5)
1 - The oxidising agent, K2C2O7 / H+ is added to a primary alchohol
2 - The orange C2O72- is reduced to green Cr3+
3 - The OH group in the alcohol is converted into a C=O group
4 - The reaction mixture turns from orange to green
5 - An Aldehyde is produced which is then oxidised into a carboxylic acid in the presence of excess oxidisning agent
What are primar, secondary and tertiary alcohols oxidised to?
1 - Primary - Aldehydes –> carboxylic acids
2 - Secondary - Ketones
3 - Tertiary - Don’t oxidise
Describe the reaction conditions for the oxidation of secondary alcohols?
Heat under reflux in the presence of an oxidising agent
In the oxidation of secondary alcolhols, why is the ketone not oxidised further?
As not enough energy can be supplied to break covalent C-C bond
Why don’t tertiary alcohols oxidise?
because they don’t have a H atom on the C to which the OH group is attched
What is the final colour of the recation mixture in the oxidation of primary, secondary + tertiary alcohols?
1 - Primary -green
2 - Secondary - green
3 - Tertoary - orange - no oxidation
What is the suffix of ketones?
One e.g propanone
What is the suffix of aldehydes?
Al e.g ethanal
What are the reaction conditions for the dehydration of alchols to alkenes? (3)
1 - Industrially - 300oc + Al2O3 catalyst
3 - Lab - conc. sulfuric acid + heat under reflux
What is meant by an elimination reaction?
A reaction where a small molecule is removed from a larger molecule leaving an unsaturated molecule
What is dehydration an example of?
An elimination reaction
What conditions are needed for the nueclophillic substituion reaction of alcohols and what is produced? (4)
1 - Alcohols undergoe nucleophillic substition with halide ions
2 - In the presence of a strong acid
3 - Halolalkanes produced
4 - water is released
What are the two ways of converting alcohols into esters?
1 - Esterfication - Using an acid anhydride - React with alcohol or phenol to form ester
2 - Esterfication - Using a carboxylic acid - Only react with alchols to form ester
Describe the reation conditions for the esterfication of alcohols using caroxylic acid? (2)
1 - Small amount of conc. sulfuric acid/ conc. HCl
2 - Heated under reflux
In the esterification of alcohols using carboxylic acid, how is the ester collected? (2)
1 - Using distillation, ester is separted from mixture
2 - Ester then purified
How are esters named?
Ethanoate
- Ethan- from ethanol
- oate - from ethanoate
Describe the esterfication of alcohols using an anhydride? (2)
1 - React completely with an alcohol on warming
2 - Gives a higher yeild of ester than esterfication with carboxylic acid
What is this called Cr2O72-
dichromate (VI)
What compounds are part of the carbonyl group?
Any compound with C=O
What type of esterfication would you use and why? (3)
1 - Using acid anhydride
2 - Because it is faster
3 - Has a higher % yeild
How are ethers similar to alcohols?
structural isomers of alcohols
How are ethers different to alcohols?
Ethers more volatile than alcohols because they have no hydrogen bonding
How do carboxylic acids react with carbonates?
Form salt, water, CO2
How do carboxylic acids react with Na carbonates? (2)
1 - Sodium salt produced
2 - Fizzes as CO2 is released
What is a phenol?
OH group on a benzene ring (C6H5OH)
How do phenols compare with alcohols?
1 - Phenols are acidic whereas alcohols are not
What are the key features of phenols? (4)
1 - Turn Universal indicator paper red
2 - Don’t react with carbonates
3 - Are acidic
4 - Don’t form esters with alcohols or acids
How do you make esters from phenols? (2)
1 - Phenols do not react with carboxylic acids
2 - Therefore phenol + acid anhydride = ester
What is the test for phenols? (2)
1 - Add neurtal FeCl3 (aq)
2 - If phenol present then it will turn purple
What are the tests for carboxylic acids? (2)
1 - Added to aqeuous solution - turns it slightly acidic
2 - React with alcohols to produce esters - (have strong fruity/flower smells)
Whar are the three different environments that hydroxyl group can occur in? (3)
1 - In COOH group in carboxylic acids
2 - Attched to a benzene ring in phenols
3 - Attched to a alkane chain in alcohols
How does an OH group react with water?
A small no. of water molecules donate H+ ions to other water molecules, the water behaves as an acid
How do OH groups reaction with water and phenols react?
Phenol + OH - The equilibirum lies further to the right than water as phenol is more acidic than water
How do carboyxlic acids + phenols react with sodium hydroxide? (2)
1 - Forms sodium salts
2 - Form water
What are alchols reactions with carbonates and hydroxyls?
They don’t
What are the two ways of esterifying salicylci acid, products and features of products?
1 - The phenol group can react with an acid anhydride
- Product = Aspirin
- Soluble in water
2 - The COOH group can react with an alcohol
- Product = methyl - 2 - hydroxybenzoate
- Lipid soluble
What is an aromatic compound?
has a benzene ring
What is an Aliphatic compound?
carbon chains without benzene rings
What is the structure for answering an exam Q on what the compound is from it’s Infared spectra?
1 - Strong absorbance at (wavenumber) which indicates (type bond) in an (compound)
2 - All this info can be taken from data sheet
Why is mass spectrometry carried out in a vaccum?
So the ions have a free path and don’t collide with air molecules
How do you produce a mass spectrum? (5)
1) Sample vaporised
2) High energy e- fired at the gas particles causing them to lose e- and become positive ions (ionisation)
3) The positive ions are accelerated by an electrical field
4) Time taken for positive ion to reach the detector is measured
- Light, highly charged ions take less time
Heavy, small charged ion take longer
5) A mass spectrum is then produced for the sample
Describe infared spectroscopy? (2)
1 - Substances are exposed to radiation
2 - This makes vibrational energy chnages occur in the molecules, which absorb infared radiation of specific frequencies
In an infared spectra, why are the frequncies absorbed different for each molecule? (2)
1 - Because the energy needed to excite a vibration depends on the bond strength
2 - Stronger bond = High frequency
What does an infared spectrometer actually do?
Detects the absorbions and produces an infared spectra
What determines the intesnity of an absorption?
More polar bond = more intense absorption
What happens when simple diatomic molecules vs complex molecules absorb infared radiation? (2)(1)
Simple
1 - The atoms pull apart and then push together - stretching
2 - For these molecules there is only one vibrational infared absorbtion which corresponds to the molecules changing from a lower vibrational energy state to a higher vibrational energy state
More complex
1 - Have many vibrational modes - rocking, tiwsting etc
What is the prupose of the fingerpirnt region in an Infared spectra?
For identification pruposes as is characteristic of that particular molecule e.g comparing it with another fingerprint region to see if the spectra is of the same compound
What can mass spectroscopy be used for?
To find out the atomic mass of elements
To fidn out the relative abundances of isotopes in an element
In mass spectroscopy, what is m/z equivilent to?
The molecular mass of the ion causing the peak
Why is the m/z value for the molecular ion useful?
Helps chemists determine the molecular mass of the compound being analysed
What is the fragmentation pattern?
The way in which a parent ion fragmets into smaller ions is characteristic of that compound
What s the base peak?
The strongest detetcor signal of 100%
What causes a peak at 1+ m/z of parent ion? (2)
Caused by the M+ ion with a C13 atom present in each ion being detected
What is the size of the M+1 peak comapred to the peak caused by the molecualr ion?
The M+1 peak is smaller as there proportionally a smaller number of C13 atoms over C12
What is the use of the fragmnetation pattern?
Allows you to identity which isomer the spectra belongs to as the fragments are characteristic of only one compound
What can an absorption spectra be used for?
To decide which fucntional groups are present in an organic molecule
What do the absorptions on an absorpion spectra represent?
They are characteristic of the bonds within the molecule
Describe the steps in recrystalisation to purify an organic solid? (4)
1 - Dissolve organic solid in a minimum amount of hot solvent
2 - filter the solution to remove insoluble inpurities
3 - Allow to cool and crystalise
4 - Vacuum filter to remove soluble impurities - Wash crytsals with cold solvent and allow to dry
What is the Mpt of an impure vs pure sample?
Pure - Sharp Mpt
Inpure - High range and Lower Mpt than pure sample as is a mixture
What is a key point in recrystalisation?
Minimum amount of hot solvent is used
What is an ideal feature of a solvent in recrytsalisation?
The organic solid dissolved in it readily when the solvent is hot
How do you carry out Mpt determination? (5)
1 - Seal the end of a capillary tube using a bunsen flame
2 - Transfer small amount of sample onto a watch glass and press the open end of the tube onto the solid
3 - This will transfer some of the solid into the cappilary tube
4 - Flick tube to get solid to bottem and place in Mpt apparatus
5 - Record the temperature which it starts and fisnihes melting at to get a Mpt range
When producing a product what are the key things you want? (4)
1 - High % yeild
2 - High atom economy
3 - Few number steps - more steps = less product
4 - How easily the product is purfied
What happens in the stationary phase?
Something doens’t move
What happens in the Mobile phase?
Something moves
In Thin layer chromotography why is pencil use?
Ink would blur and move
In TLC what is the stationary phase?
The plate
In TLC what is the mobile phase?
The solvent/liquid
Describe TLC chromotography? (8)
1 - Draw a pencil line 5mm from bottom of plate
2 - Dot the samples on seperate spots on the line
3 - Place plate in a beaker with solvent below the pencil line
4 - Put a lid on the beaker - stop solvent evaporating
5 - Allow solvent to travel up the plate, taking it out before it reaches the top
6 - Mark solvent front + dry plate
7 - Develop uisng I2 crystals or by U.V radiation
8 - Calulate Rf values
What does similar R.F values mean?
The samples are the same compound
How dou identify fragments with a lower mass? (2)
1 - They are usually due to small fragments of the hydrocarbon chain in the original molecule
How do you identify fragments with larger masses?
1 - Look at the difference between the mass of this peak and the mass of the M+ peak
What is the definition for the molecular ion?
An ion formed by the removal of an e- from a molecule without fragmentation of the molecular structure.
In mass spectroscopy why are some peaks higher than others? (2)
1 - It’s the commonest fragment because:
- There are sereval ways it can be produced
- It’s the most stable ion
2 - This results in a higher peak
What is green chemisrty?
Developing chemical products and processes that are environmentaly friendly and sustainable
What are the 12 key pricniples of green chemisrty?
1 - Better atom economy - more product, less waste
2 - Prevention of waste products -
3 - Less hazardous chemical synthesis - use less hazardous reagants
4 - Design safer chemical products -
5 - Use safer solvents - minimise use of organic solvents
6 - Low energy usage - lower temp + pressure
7 - Use renewable feedstocks
8 - Reduce reagants used + no. steps
9 - Use catalysts + more selective catalysts - these reduce energy usage + waste
10 - Design chemical products for degradation - should break down
11 - Employ real time process monitoring - this reduces waste
12 - Use safer chemical processes
What are some downfalls of the implemeting the 12 key pricnples of green chemistry? (3)
1 - Are less hazardous reagnts more expensive
2 - Is the new reagnat used to increase atom economy, more hazaroud
3 - Lower temp decrease reaction rate
What can TLC be used for? (3)
1 - Seperate small quantities of organic compounds
2 - Check the purity of organic substances
3 - Follow the progress of a reaction over time
How do you know whether a compound is pure is Mpt detrmination?
The compound should melt within 0.50c of it’s published true Mpt
What is Mpt dtermination used for? (2)
1 - To measure how pure a sample is
2 - Help identiy a sample
What’s a carbonyl compound?
Contains a O=
What is meant by heating under reflux?
Liquid boiled, condensed and returned to flask
