TXTBK: What's in a medicine Flashcards
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What is the general formula of the homologous series ethers?
- ROR’
- Have the same molecular formula as alcohols but have a different structure - they are structural isomers to alcohols
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What is the structural formula of the homologous series ethers?
- R-O-R’
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What is the prefix of the homologous series ethers?
- -oxy-
- e.g. methoxyethane
- When naming an ether, the longer hydrocarbon chain is chosen as the parent alkane
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How are ethers derived?
- from alkanes by substituting an alkoxy group (-OR) for a hydrogen atom on the alkane
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What does the R represent in general or structural formulas?
- R in formula represents an alkyl group, which is an alkane that’s missing one hydrogen atom
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What is the general formula of the homologous series ketones?
- RCOR’
- contains a carbonyl group C=O
- carbonyl group is within the alkane chain
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What is the structural formula of the homologous series ketones?
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What is the suffix of the homologous series ketones?
- -one
- e.g. propanone
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What is the general formula of the homologous series aldehydes?
- RCHO
- contains a carbonyl group, C=O
- is at the end of the alkane chain
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What is the structural formula for the homologous series aldehydes?
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What is the suffix of the homologous series aldehydes?
- -al
- e.g. ethanal
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What is the general formula of the homologous series esters?
- RCOOR’
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What is the structural formula of the homologous series esters?
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What is the suffix of the homologous series esters?
- -oate
- e.g. ethyl methanoate
- Esters are named from the alcohol and acid that form them
- ‘ethyl’ from ethanol
- '’methanoate’ from methanoic acid
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What is the general formula of the homologous series carboxylic acids?
- RCOOH
- contain the carboxyl group
- two O2 atoms not joined together
- remainder of molecule may be an alkyl group or carboxyl group may be attached to a benzene ring
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What is the structural formula for the homologous series carboxylic acids?
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What is the suffix of the homologous series carboxylic acids?
- -oic acid
- e.g. ethanoic acid
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What is the general formula of the homologous series acid anhydrides?
- (RCO)2O
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What is the structural formula of the homologous series acid anhydrides?
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What is the suffix of the homologous series acid anhydrides?
- -oic anhydride
- e.g. ethanoic anhydride
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What is the general formula of the homologous series alcohols?
- ROH
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What is the structural formula of the homologous series alcohols?
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What is the suffix of the homologous series alcohols?
- -ol
- e.g. ethanol
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What are the three types of alcohols?
- functional group in the alcohol homologous series is the hydroxy group, -OH
- type of alcohol depends on which carbon atom the -OH group is bonded to
- types:
- primary alcohols
- secondary alcohols
- tertiary alcohols
- reactions of alcohols depend on the type of alcohol involved
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Describe the position of the -OH group on a primary alcohol
- -OH group bonded to a carbon atom that is bonded to only one other carbon atom
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Describe the position of the -OH group on a secondary alcohol
- -OH bonded to a carbon atom that is bonded to exactly two other carbon atoms
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Describe the position of the -OH group on a tertiary alcohol
- -OH group bonded to a carbon atom that is bonded to exactly three other carbon atoms
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What is the general formula for a primary alcohol?
- RCH2OH
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What is the general formula for a secondary alcohol?
- RCH(OH)R’
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What is the general formula for a tertiary alcohol?
- R2C(OH)R’
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What type of alcohol is butan-1-ol?
- primary
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What type of alcohol is butan-2-ol?
- secondary
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What type of alcohol is 2-methylpropan-1-ol?
- tertiary
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What is the test for a phenol?
- neutral iron(III) chloride solution
- shake - if positive - goes purple
- the -C=C-OH group (called the enol group) can form a purple complex with Fe3+ ions in neutral solution
- a complex - when a group of atoms become attached to a metal ion
- Only phenol and its derivatives have such an arrangement of atoms and are the only ones to give colour with neutral iron(III) chloride solution
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What is the purpose of green chemistry?
- to develop chemical products and chemical processes that are as sustainable and as environmentally friendly as possible
- sustainable chemistry (green chemistry) means not using up all tje Earth’s resources, or putting loads of damaging chemicals into the environment
- as a result not ruining things for future generations
- Chemists came up with green chemistry principles which help chemical industries to become more sustainable
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What are the key principles of green chemistry that come under using renewable sources?
Use renewable resources
- Use renewable raw materials where possible (renewable feedstocks - instead of depleting natural resources)
- e.g. some plastics now made from plant products instead of non-renewable crude oil fractions
- Use renewable energy sources
- e.g. many chemical processes use energy from fossil fuels which will run out. Solar panels and bioethanol from plants are some alternatives
- if it’s not possible to use energy from renewable sources then minimise energy usage
- by lowering temperature and pressure in processes
- saves money, reduces production of pollution and helps prolong fossil fuel resources
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What are the three foundations of green chemistry?
- Using renewable resources
- Ensuring all chemicals and processes involved are as safe as possible
- Making sure that waste is minimised and products are biodegradable or recyclable
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What are the key principles of green chemistry that come under ensuring all the chemicals and processes involved are as safe as possible?
Ensure all the chemicals processes involved are as safe as possible
- chemical reations should be designed to use and produce substances which are non-toxic and not harmful to humans or the environment
- design safer chemical products - less toxic and hazardous chemicals
- less hazardous chemical synthesis (reactants) - using less hazardous chemicals in the chemical reaction
- use safer solvents - minimise use of organic solvents
- use safer chemical processes - choose processes that minimise potential risk of accident such as releasing gases, fires and explosions
- technologies and methods for monitoring and controlling processes which involve hazardous substances, should be improved
- employ real time process monitoring
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What are the key principles of green chemistry that come under making sure that waste is minimised and products are biodegradable or recyclable?
- prevention of waste products
- better to prevent wate than treating and disposing after its been created
- increase atom economy - as high as possible
- means more of the feedstock is turned into products and less waste products are produced
- use catalysts and more selective catalysts
- reduces amount of reagents needed for reaction, reduces energy and waste products
- reduce reagents used and the number of steps
- to prevent waste
- design chemical products for degradation
- chemical products should be biodegradable (break down into innocuous products and don’t hang around the environment for a long time) or recyclable
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Why does acidified potassium dichromate(VI) change colour during oxidation?
- goes from orange to green
- because with oxidation of primary and secondary alcohols, the orange dichromate(VI) ion, Cr2O72-(aq), is reduced to green chromate(III) ions, Cr3+(aq)
- tertiary alcohols don’t oxidise to anything - dichromate(VI) ion not reduced and therefore there is no colour change - stays orange
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What is the homologous series that is displayed below
- primary alcohol
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What is the homologous series that is displayed below? What would it be called?
- primary alchol
- propan-1-ol
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What is the homologous series that is displayed below?
- secondary alcohol
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What is the homologous series that is displayed below? What would it be called?
- secondary alcohol
- propan-2-ol
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What is the homologous series that is displayed below?
- tertiary alcohol
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What is the homologous series that is displayed below? What would it be called?
- tertiary alcohol
- 2-methlpropan-2-ol
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What are primary alcohols oxidised to?
- aldehydes
- then carboxylic acids
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What are secondary alcohols oxidised to?
- ketones
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What are tertiary alcohols oxidised to?
- don’t oxidise into anything
- acidified potassium dichromate(VI) stays orange - not reduced
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What is formed from the dehydration of alcohols?
- alkenes by elimination of a water molecule in a dehydration reaction
- described as dehydration - because water molecule removed
- dehydration is an example of an elimination reaction - reverse of addition reaction
- in an elimination reaction - small group of atoms break away from a larger molecule. The small group is not replaced by anything else.
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What are the two methods of dehydrating alcohols?
- reflux with concentrated sulfuric acid
- using heated Al2O3
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Identify the type of reaction below:
C2H5OH –> CH2=CH2 + H2O
- dehydration reaction, example of elimination
- to form alkene from alcohol by loss of water molecule
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What is the definition of an elimination reaction?
- A reaction where a small molecule is removed from a larger molecule and not replaced by anything else leaving an unsaturated molecule. In the case of alcohols the small molecule is water
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Identify the reaction below:
- dehydration reaction, example of elimination
- to form alkene from alcohol by loss of water molecule
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Write an equation for the dehydration of propan-1-ol. Draw the full displayed formula for any organic compounds.
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Write an equation for the dehydration of propan-1-ol. Draw the skeletal formula for any organic compounds.
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Identify the reaction below:
- dehydration reaction, example of elimination
- to form alkene from alcohol by loss of water molecule
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How are alcohols dehydrated using heated Al2O3?
- Alcohol vapour is passed over a hot/heated catalyst of pumice stone or aluminium oxide Al2O3 at 300oC
- catalyst provides a large surface area for the reaction
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How are alcohols dehydrated under reflux using concentrated sulfuric acid?
- reflux alcohol with excess concentrated sulfuric acid at 170oC
- ethene produced then collected over water
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Describe and explain the mechanism for the dehydration of alcohols under reflux using concentrated sulfuric acid
- concentrated sulfuric acid acts as a dehydrating agent in the elimination reaction
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How is a haloalkane formed from an alcohol?
- alcohol reacts with compound containing halide ions (such as HCl, HBr, but also may be carried out with different halide molecules - NaBr) in a nucleophilic substitution reaction
- the hydroxyl (-OH) group is replaced by the halide, so acohol is transformed into a haloalkane
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Identify the reaction below:
CH3CH2CH2CH2OH + H+ + Br- –> CH3CH2CH2CH2Br + H2O
- nucleophilic subsititution reaction
- forming a haloalkane from an alcohol
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Name the reactants and products of the reaction below and identify the type of reaction
- alcohol - 2-methylpropan-2-ol
- haloalkane 2-chloro-2-methylpropane
- nucleophilic substitution reaction
- to make 2-chloro-2-methylpropane - just need to shake 2-methylpropan-2-ol (a tertiary alcohol) with hydrochloric acid
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What are the two ways of converting alcohols into esters?
- esterification using a carboxylic acid
- esterification using an acid anhydride
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What type of reaction is esterification between an alcohol and carboxylic acid?
- also a condensation reaction as it releases water
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How is an ester made using a carboxylic acid?
- esterification
- alchol + carboxylic acid ⇌ ester + water
- reaction occurs extremely slowly unless strong acid catalyst present
- small amount of either concentrated sulfuric acid or concentrated hydrochloric acid = generally used
- reaction mixture (acid catalyst + alcohol + carboxylic acid) heated under reflux
- esterification with carboxylic acid = reversible reaction (use ⇌)
- eventually comes to an equilibrium - means both reactants and products present
- ester would need to be separated from the mixture using distillation and purified
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Identify the general reaction below:
- esterfication between alcohol and carboxylic acid to form ester and water
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Write the equation and skeletal formula for the making ethyl ethanoate using ethanoic acid
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How is an ester made using an acid anhydride?
- esterification
- alcohol + acid anhydride –> ester + carboxylic acid
- acid anhydride (derivatives of carboxylic acids) are more reactive than a carboxylic acid and react completely with an alcohol on warming to give a much higher yield of ester
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Identify the general reaction below:
- esterification between alcohol and acid anhydride to form an ester and a carboxylic acid
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Write a reaction to form ethyl ethanoate using ethanoic anhydride
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What is the purpose of chromatography?
- (TLC) used to separate small quantities of organic compound mixtures - ideal for identifying what makes up a mixture
- can also use chromatography to separate large quantities of a mixture in an organic synthesis
- (can be used to separate the desired product from unreacted chemicals or side products )
- purify
- check purity of organic substances
- follow the progress of a reaction over time
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How can chromatography be used to separate large quantities of a mixture
- chromatography to separate large quantities of a mixture in an organic synthesis
- (can be used to separate the desired product from unreacted chemicals or side products )
- need much larger scale equipment - glass column (e.g. burette) packed with silica or alumina (same stationary phase used in TLC)
- you then pour your mixture into the column and run solvent (the mobile phase) through it continually
- the different chemicals in the mixture move down the column at different rates, so they come out at different times, meaning you get pure chemicals
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What is specific to thin layer chromatography instead of other types of chromatography?
- Chromatography carried out using a silica or alumina plate
- thin layer of silica (silicon dioxide) or alumina (aluminium oxide) fixed to a glass or metal plate
- the thin layer is the stationary phase
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What is the same for all types of chromatography?
- many different types of chromatography
- all involve a mobile phase (a liquid or gas) that moves over a second material called the stationary phase (which doesn’t move)
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How is thin layer chromatography able to separate mixtures?
- thin layer chromatography (TLC) relies on different organic compounds having different affinities for a particular solvent
- suitable solvent must be chosen
- so different organic compounds will be carried through the chromatography medium (plate) at different rates
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Describe the method of how thin layer chromatography is carried out
- In thin layer chromatography (TLC), the stationary phase is a thin layer of silica (silicon dioxide) or alumina (aluminium oxide) fixed to a glass or metal plate
- Draw a thin baseline in pencil 1cm from the bottom of thin layer chromatography plate
- pencil is used because it will not run into the solvent
- Spot a small drop of your test sample on the baseline as well as reference samples separated on the line
- Place the plate in a beaker containing a small volume of solvent (this is the mobile phase) making sure the plate is suspended and does not touch the bottom of the beaker
- the solvent level must be below the baseline
- Cover the beaker with a watch glass
- to prevent the solvent from evaporating
- Leave the beaker until the solvent front is near the top
- As it moves up the plate, the solvent will carry the substances in the mixture with it - but because of different affinities some chemicals will be carried faster than others and so travel further up the plate
- Then remove the plate from the beaker and mark how far the solvent front has travelled up the plate before it evaporates and allow to dry
- The chromatogram produced will not show the organic compounds as they are all colourless and therefore spots will need to be located using iodine, ninhydrin, or using an ultraviolet lamp
- You can use the positions of the chemicals on the chromatogram to identify what the chemicals are by matching the heights reached, or Rf values with those of known compounds
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Give details of how organic chemicals are revealed using UV light in thin layer chromatography
- Organic compounds are colourless and therefore need to be revealed
- Many TLC plates have a special fluorescent dye added to the silica or alumina layer that glows when UV light shines on it
- Where there are spots of chemical on the plate, they cover the fluorescent dye and don’t glow
- You can put the plate under a UV lamp and draw around the dark patches to show where the spots of chemicals are
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Give details of how organic chemicals are revealed using iodine vapour in thin layer chromatography
- Organic compounds are colourless and therefore need to be revealed
- Way of exposing position of spots is to use iodine vapour
- Leave the plate in a sealed jar with a couple of iodine crystals
- Iodine vapour is a locating agent - it sticks to the chemicals on the plate and they’ll show up as purple spots
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In what case does the chemicals on a plate in thin layer chromatography not need to be revealed?
- if the chemicals in the mixture are coloured
- e.g. dyes that make up ink
- dot of different colours at different heights on the TLC plate
- organic compounds are all colourless - and need to be revealed
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Give details of how thin layer chromatography can be used to help identify substances
- if you just want to know how many chemicals are present in a mixture, all you have to do is count the number of spots that form on the plate
- but if you want to find out what each chemical is, you can calculate something called an Rf value
- Rf = distance travelled by spot / distance travelled by solvent
- Rf values are always the same no matter how big the plate is or how far the solvent travels - because these are properties of the chemicals in the mixture and so can be used to identify those chemicals
- But if the composition of the TLC plate, the solvent, or the temperautre changes even slightly, you’ll get a different Rf value
- It is hard to keep the conditions identical
- so if you suspect that a mixture contains a chemical, it is best to put a spot of that chemical on the baseline of the same plate of the test sample and run them both at the same time
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What organic compounds contain a hydroxyl, -OH, group?
- as part of a carboxyl group in carboxylic acids
- attached to an alkane chain in alcohols
- three types of alcohols = primary, secondary, tertiary - according to position of the -OH group
- attached to a benzene ring as phenols
- although phenols look similar to alcohols, they behave very differently (generally true that functional groups behave differently when attached to an aromatic ring compared to when attached to alkyl group)
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What are the three most frequently used instrumental techniques of the analysis of chemicals?
- infrared (IR) spectroscopy
- nuclear magnetic resonance (nmr) spectroscopy
- mass spectroscopy
