F334: What's in a medicine?

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What is an acid according the Bronsted-Lowry theory?
An acid is a proton donor.
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What is a base according to the Bronsted-Lowry theory?
A base is a proton acceptor.
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What is a hydrogen ion?
A proton - when a hydrogen loses an electron all that is left is a proton
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How doe acids and bases react?
They transfer protons - hydrogen ions move from the acid to the base.
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What holds ions together in ionic bonding?
Electrostatic attraction
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How are ions formed?
Electrons are transferred from one atom to another - atoms want to lose or gain electrons so that they have a full outer shell.
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What structure do ions form?
Regular lattice.
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What type of structure to metals form?
Giant metallic lattice.
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How does metallic bonding work?
A metal atom loses its outer shell electrons, becoming a positive ion. The electrons that are removed from the outer shell form a sea of delocalised electrons. The positive ion and electrons attract each other to from a lattice.
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What is covalent bonding?
When two atoms share electrons, so that they both have a full outer shell of electrons. Both the positive nuclei are attracted electrostatically to the shared electrons.
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What is another name for a dative covalent bond?
A coordinate bond.
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What is a dative covalent bond?
One atom donated both the electrons to a bond.
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Name an element that can form giant networks of covalently bonded atoms?
Carbon - graphite and diamond
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What are the properties of ionic bonding?
High melting and boiling points, solid at STP, does not conduct electricity solid but does when liquid and is soluble in water.
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What are the properties of simple molecular (covalent) bonding?
Low melting and boiling points, sometimes solid at STP but usually liquid or gas, does not conduct electricity at all and is soluble in water depending on how polarised the molecule is.
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What are the properties of giant molecular (covalent) bonding?
High melting and boiling points, solid at STP, does not conduct electricity as a solid (except graphite) and usually sublimes. It is insoluble in water.
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What are the properties of metallic bonding?
High melting and boiling points, solid at STP, conducts electricity when solid and liquids and is insoluble in water.
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Why can't a substance that has ionic bonds conduct electricity when solid but can when liquid?
The ions are held firmly in place in a solid but are free to move in a liquid so they can pass charge, and therefore are able to conduct electricity.
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Why do molecules that have simple molecular (covalent) bonds have low boiling and melting points?
You only have to overcome the intermolecular forces not the intramolecular forces (covalent bonds).
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What does the shape of a molecule depend on?
The number of electron pairs in the outer shell of the central atom.
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Where will you find the greatest angle in a molecule?
Angles between two lone pairs of electrons are the greatest as lone pairs repel more than bonding pairs.
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What shape would a molecule with two groups of electrons around the central atom be and what angle would it have?
Linear - 180 degrees
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What shape and bond angle would a molecule with 3 groups of electrons around the central atom have?
Trigonal planar - 120 degrees
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What shape and bond angle would a molecule with 4 groups of electrons have?
Tetrahedral - 109.5 degrees (if all the electron pairs are bonding pairs). Trigonal pyramidal - 107 degrees (one lone pair). Bent - 104.5 degrees ( 2 lone pairs).
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What shape and bond angle would a molecule with 5 groups of electrons around the central atom have?
Trigonal bipyramidal - 90 and 120 degrees (no lone pairs)
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What shape and bond angle would a molecule with 6 groups of electrons around the central atom have?
Octahedral - 90 degrees (no lone pairs)
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What functional group do arenes have?
Benzene ring
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What functional group do ethers have?
C-O-C
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What conditions do you need to produce an alkane from an alkene?
Hydorgen (H2), nickel catalyst, 150 degrees celcius, high pressure OR platinum catalyst at RTP
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What conditions do you need to produce alcohol form an alkene?
Steam, 300 degrees celcius, phosphoric acid catalyst (H3PO4) OR water, concentrated sulfuric acid catalyst (H2SO4)
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What conditions do you need to produce an alkene from an alcohol (dehydration)?
Aluminium oxide (Al2O3) at 400 degrees celcius OR reflux with concentrated sulfuric acid (H2SO4)
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What conditions do you need to produce a carboxylic acid from an alcohol?
Reflux primary alcohol with acidified potassium dichromate
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What conditions do you need to produce a ketone from an alcohol?
Reflux secondary alcohol with acidified potassium dichromate
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What conditions do you need to produce an aldehyde from an alcohol?
Gently heat primary alcohol with acidified potassium dichromate with distillation
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What conditions do you need to produce a carboxylic acid from an aldehyde?
Reflux with acidified potassium dichromate
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What conditions do you need to produce an alcohol from a chloroalkane?
Reflux with aqueous sodium hydroxide (nucleophilic substitution)
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What conditions do you need to produce a chloroalkane from an alcohol?
Shake with concentrated hydrochloric acid at room temperature (tertiary alcohols only)
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What conditions do you need to produce an amine from a chloroalkane?
Reflux with excess ammonia (NH3) in ethanol solvent
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What is the process of forming a poly(alkene) from an alkene?
Free radical polymerisation
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What conditions do you need to produce a dibromoalkane from an alkene?
Bromine (Br2), 20 degrees celcius (electrophilic addition) - bromine water is decolourised, it's the test for an alkene
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What conditions do you need to produce a bromoalkane from an alkene?
Hydrogen bromide (HBr), 20 degrees celcius (electrophilic addition)
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What functional group do carboxylic acids contain?
-COOH
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What is a dicarboxylic acid?
When there are two carboxy (-COOH) functional groups, one on either end of the molecule
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Carboxylic acid is what type of acid and why?
Weak acid - in water they partially dissolve into a carboxylate ion and a hydrogen ion. The equilibrium lies to the left as most of the molecule does not dissociate
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What happens when a carboxylic acid reacts with an aqueous alkali?
It is neutralised and forms a salt and water
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What happens when a carboxylic acid reacts with an carbonate or hydrogencarbonate?
Salt, carbon dioxide and water are formed
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What are esters made from?
Carboxylic acids and alcohols
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What is the functional group of an ester?
-COO-
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What conditions do you need to form an ester?
An alcohol and a carboxylic acid need to be heated in the presence of an acid catalyst (usually concentrated sulfuric acid).
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What is the name of the reaction that forms esters?
Esterification reaction
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What are the products of the reaction between a carboxylic acid and an alcohol?
Ester and water
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What is a phenol?
The aromatic versions of alcohols. A benzene ring with an -OH group attached.
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What is an aliphatic compound?
A compound that doesn't contain a benzene ring
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Why is benzene not as reactive as you might expect?
It has a delocalised ring of electrons due to each carbon having one spare electron in its outer shell which isn't used for bonding. Delocalisation makes benzene more stable.
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How do you test for a phenol?
Add iron (iii) chloride solution and shake - it turns purple in the presence of phenol.
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Can a phenol dissolve in water?
Phenol dissolves a little bit in water, as the -OH group is able to form hydrogen bonds with water molecules. The solution is weakly acidic because phenol dissociates in water to form a phenoxide ion and a hydrogen ion.
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What happens when a phenol reacts with a strong base?
A salt is formed. Phenol reacts with sodium hydroxide solution at RT to form sodium phenoxide and water. Phenol doesn't react with sodium carbonate as it is not a strong enough base - can't remove the hydrogen ion from the phenol.
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What is the functional group of acyl chlorides?
-COCl
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What happens when an acyl chloride reacts with an phenol?
An ester is formed.
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What is an advantage of using an acyl chloride instead of a carboxylic acid when making an ester?
Phenols react very slowly with carboxylic acid, so it is faster to use an acyl chloride instead.
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How do you reflux something?
Heat the mixture in a flask fitted with a Liebig condenser, which condenses the vapours and recycles them back into the flask giving them time to react.
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How do you distil something?
Heat the impure liquid in a flask fitted with a thermometer and a condenser. When the liquid you want boils (it's at its boiling point on the thermometer) you place a flask at the open end of the condenser and collect your product.
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What is a hydrogen cyanide?
A weak acid - it partially dissociates in water to from hydrogen ions and cyanide ions (CN-)
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What is the mechanism in which hydrogen cyanide will react with carbonyls?
Nucleophilic Addition - the cyanide ion attacks the partially positive carbon atom and donates a pair of electrons. 2 electrons from the double bond transfer to the oxygen; H+ bonds to the oxygen froming -OH
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What safety precautions need to be taken when working with hydrogen cyanide?
Hydrogen cyanide is a highly poisonous gas, so the reaction must be carried out in a fume cupboard.
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What is a rearrangement reaction?
No atoms are added or removed. The atoms just change the order in which they're connected.
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What is an addition reaction?
Molecules add together.
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What is a substitution reaction?
One functional group is 'swapped' for another.
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What is an elimination reaction?
Atoms are removed from a molecule.
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What is a condensation reaction?
This is addition followed by elimination.
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What reaction types have the highest (100%) atom economy?
Addition and rearrangement
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What reaction type has the lowest atom economy?
Elimination
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What is combinatorial chemistry?
Making hundreds of similar compounds all at once and then testing them to see if any are effective.
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What three questions need to be answered in clinical trials?
Is it safe? Does it work? Is it better than anything currently available?
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What is an advantage of having a high atom economy?
More environmentally friendly - you don't need as many natural resources and there won't be as much (if any) waste.
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How does infrared spectroscopy work?
A beam of IR radiation goes through the sample, the IR radiation is absorbed by the bonds, increasing their vibrational energy. Different bonds absorb different wavelengths. Bonds in different places in a molecule also absorb different wavelengths.
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What technique can be used to separate and identify molecules?
Chromatography
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How can you identify the molecules in thin layer chromatography?
You can use their positions on the plate to identify what chemicals they are.
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How will you identify colourless chemicals?
You can use UV light or expose the plate to iodine vapour and the chemicals will show up as purple dots.
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How can chromatography be used to purify substances?
Gas chromatography can be used to purify chemicals. 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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How do you use chromatography to identify how many chemicals are present?
Count the number of dots on the plate.
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How do you work out the Rf value?
Distance travelled by spot/distance travelled by solvent
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How do you calculate the 'lost' fragments from mass spectroscopy?
Look at the difference between two peaks on a mass spectrum.
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Why are accurate measurements of m/z values on a mass spectrum useful?
They allow you to compare elements and compounds using relative isotopic masses.
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How do you break a molecular ion into fragments for mass spectroscopy?
Electron bombardment.
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Card 2

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What is a base according to the Bronsted-Lowry theory?

Back

A base is a proton acceptor.

Card 3

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What is a hydrogen ion?

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Card 4

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How doe acids and bases react?

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Card 5

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What holds ions together in ionic bonding?

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