Flashcards in Unit 4 Deck (181):
What is made when an aromatic compound and an acyl chloride react? What is the catalyst and how does it work?
An acyl substituted arene is produced (e.g. phenylethanone) and AlCl3 is the catalyst, taking the Cl- from the acyl chloride to make AlCl4-
What is the prefix meaning benzene?
How do you make an Acyl chloride from a carboxylic acid
Why does increasing temperature increase rate of reaction?
A greater proportion of particles have the activation energy
What values do you need to work out the equilibrium constant, Kc?
The CONCENTRATIONS of reactants and products.
In what situation can you use moles to calculate the equilibrium constant?
When the top and bottom of the Kc equation are the same order, so units and volumes would cancel out.
Products increase, reactants decrease. Left or right?
Reactants increase, products decrease. Left or right?
What is the only factor that affects the equilibrium constant?
What does it mean if Kc is greater than 10^10? What about 10^-10?
Large Kc: reaction regarded as going to completion. Small Kc: reaction regarded as not taking place at all.
What is H3O+ called?
The oxonium/hydronium/hydroxonium ion
What is Kw?
The ionic product of water. Kc x [H2O(l)]
Why is water not included in the formula for Kw?
It is constant so already accounted for in Kw (Kc x [H2O(l)])
What is formed when solid sodium halide reacts with concentrated sulfuric acid in the cold?
Hydrogen halide and NaHSO4
Which halide ions can reduce sulfuric acid and what are the products?
Br- and I- are oxidised to make Br2 and I2. H2SO4 is reduced to SO2 gas, then I- oxidises it further to S and H2S.
What's the trend of solubility of group 2 hydroxides?
More soluble down the group. Mg(OH)2 is very slightly soluble. Ca(OH)2 is limewater.
What's the trend of solubility of group 2 sulfates?
Decreases down the group. Barium ions are used as a test for sulfate ions because a white precipitate is produced.
What is the equivalence point
The steep bit on a pH curve where the solution is (sort of) neutral
What's special about the half neutralisation point?
Ka is equal to [H+] because [A-]=[HA] therefore pKa=pH
What is a buffer solution?
A solution that can resist changes of acidity or alkalinity. When small amounts of acid or alkali are added to them, their pH remains almost constant.
How does an acidic buffer work?
Concentrations of HA and A- are big so they can react with added OH- or H+ and the ratio doesn't change much so H+ concentration remains almost constant.
Apart from adding a salt, how can an acidic buffer be made?
Neutralising some of the acid with a base so there is a supply of A-. If half the acid is neutralised the buffer has a pH equal to the pKa and is equally efficient at resisting acids and alkalis.
How does a basic buffer work?
The alkali removes added H+ and its salt removes added OH-
What is the ending for double bond
What is the ending for triple bond
What is the ending for esters?
What is the ending for amides
What is the ending for nitriles
What are anhydrides
Like double carboxylic acids joined by O=C-O-C=O
What's the ending for anhydrides
What's the ending for aldehydes
What's the ending for ketones
What's the ending for amines
What's the prefix for amines
What's the prefix for alcohols
What's the prefix for a ring
How can an isomer be structural
Different functional group, functional group attached at different point in the chain, or different arrangement of carbons in the skeleton.
Same structural formula but different arrangement of atoms and bonds in space.
What is the central atom of an optical isomer called?
What is a pair of optical isomers called?
How is optical rotation measured
With a polarimeter
Which direction does the + isomer rotate plane polarised light
Which direction does the - isomer rotate plane polarised light?
What are other ways of notating + and - isomers?
R and S; D and L
What must you remember when naming alkenes?
E or Z
How does priority work with E and Z isomers
Go one atom out each time and the greater mass has priority
What is a 50:50 mixture of enantiomers called?
A racemate/racemic mixture
Why do certain reactions produce a racemic mixture?
The starting molecule is planar so can be attacked equally from either side.
Why does nature usually only form one enantiomer?
Molecules are produced using enzyme catalysts
What is the compound called which has CHO attached to a benzene ring?
Benzenecarbaldehyde (sometimes referred to as benzaldehyde)
What is the suffix for an aldehyde bonded to a benzene ring?
Carbaldehyde, and the carbon isn't counted as part of the root name
Compare boiling points of alkanes, alcohols and ketones
Ketones are strongly polar so they have stronger dipole dipole forces than alkanes, but alcohols have the highest boiling points due to hydrogen bonding.
How do strong oxidising agents affect ketones?
They break the hydrocarbon chain giving a shorter chain molecule, carbon dioxide and water.
What is in Fehling's A and Fehling's B?
A: Cu2+ ion. B: alkali and complexing agent.
What is in Tollen's reagent and what does it do?
[Ag(NH3)2]+ (from ammonia and silver nitrate) which oxidises the aldehyde while the Ag2+ is reduced to solid silver.
What is Benedict's solution?
Like Fehling's but isn't prepared by mixing and has a different completing agent
What is a completing agent?
A species that can form coordinate bonds with metal atoms/ions
How do you say NaBH4
What type of reaction is reduction with [H]?
Nucleophilic addition (because H- is a nucleophile. H+ comes later)
What is it called when a benzene ring is bonded to methanoic acid?
Benzenecarboxylic acid (often called benzoic acid)
Explain the melting points of carboxylic acids
High because they form hydrogen bonds in the solid state.
What is the triangular-ish tube called for melting point analysis?
What is a Thiele tube for?
In melting point analysis, oil circulates the tube by convection (heated in the sticking-out bit) so the sample is heated in a slow and controlled manner.
Where is the sample kept in Thiele tube melting point analysis?
In a capillary tube attached to the thermometer.
What's the freezing point of ethanoic acid?
What happens to a carboxylic acid when the hydrogen delocalises?
The negative charge on the carboxylate ion is shared in a U shape across the whole group, between the two Os with a C in the middle, which makes it more stable
What is the formula of sodium ethanoate
What is the generic name for carboxylic acid salts?
What is the difference between acid and base catalysed hydrolysis of esters?
Base goes on to react with the carboxylic acid which makes a salt, which drives the reaction forward (shifts the equilibrium) so more is hydrolysed, but it produces soap which might not be wanted. Acid doesn't do that.
How are esters formed from carboxylic acids?
Carboxylic acid reacts with an alcohol to make ester and water, and an equilibrium is set up. A strong acid catalyst speeds up the reaction, e.g. sulfuric acid, but it doesn't change the composition of the equilibrium mixture.
How is an ester separated from a carboxylic acid and alcohol?
It is more volatile so can be distilled off.
How does hydrolysis of esters work
The carbonyl C has a δ+ charge so can be attacked by water acting as a weak nucleophile.
What is the proper name of glycerol?
What's the difference between a fat and an oil?
Oils are liquid at room temperature, fats are solid.
What functional group do fats and oils belong to?
What do you get by boiling triglycerides with sodium hydroxide?
Glycerol and a mixture of sodium salts of the three acids from the ester. The sodium salts are soaps, and the type depends on the fatty acids.
Why do sodium salts created from hydrolysis of triglycerides work as soap?
The carboxylate ions have a long hydrocarbon chain which is non polar but the COO- group is polar and ionic, so the hydrocarbon mixes with grease while the COO- mixes with water. Yay, you have an emulsifier!
What are some uses of glycerol?
It has three O-H bonds so forms hydrogen bonds with water, therefore is used to prevent pharmaceutical/cosmetic ointments and creams from drying out. It's a solvent in many medicines, and is present in toothpastes. It's a solvent in the food industry, e.g. food colourings. It's a plasticiser - introduced between polymer molecules, allowing them to slip over each other making the material flexible and smooth. (Over time plasticiser leaks away and the plastic becomes brittle and inflexible)
How is biodiesel made from plant oils?
The oil (triglyceride ester) is reacted with methanol which makes methyl esters and and glycerol. The methyl esters can be used as fuel in diesel vehicles.
What is the acyl group?
What is the ending for an acid chloride?
What's the catch when naming dioic acids?
There's an "e" in there, e.g. Butanedioic acid
What is a nucleophile?
A species with a lone pair of electrons. It attacks positively charged carbon atoms.
What happens when a nucleophile attacks a carbonyl group?
It replaces the random thing (like H in a carboxylic acid) and thus the nucleophile is acylated.
What does the readiness of acylation depend on?
The magnitude of δ+ charge on the carbonyl carbon (which depends on the electronegativity of Z); how easily Z is lost (Z = the leaving group); and how good the nucleophile is.
Which are better acylating agents, acyl chlorides or acid anhydrides?
The first one.
Water, ammonia, alcohol and primary amine. List in order of best to worst nucleophile.
Primary amine, ammonia, alcohol, water.
What do you get from ammonia reacting with an acid chloride or anhydride?
What do you get from an amine reacting with an acid chloride or anhydride?
What do you get from an alcohol reacting with an acid chloride or anhydride?
What do you get from water reacting with an acid chloride or anhydride?
What are the advantages of ethanoic anhydride over ethanoyl chloride?
Cheaper, less corrosive, does not react with water as readily, and has a safer by-product (weak not strong acid)
What are the carbon-carbon bond lengths in benzene?
Shorter than C-C but longer than C=C
What happens to the electrons in benzene?
They are delocalised and form a region of electron density above and below the benzene ring.
Why does Kekulé's structure of benzene not work?
A cyclic triene should show addition reactions, which benzene rarely does. The structure would also lead to isomers of some molecules e.g. if two groups were substituted adjacently, however benzene does not.
What is benzene at room temperature?
A colourless liquid
Why do benzene and hexane have such different melting points?
Benzene molecules can pack together better therefore are harder to separate.
How do aromatic compounds react and why?
Mostly by electrophilic substitution because the ring is an area of high electron density so is attacked by electrophiles, aromatic ring is very stable so almost always remains intact. (The energy to break the ring is called the delocalisation energy)
What is notable about combustion of arenes?
The flame is smoky because there is a high carbon:hydrogen ratio so there is usually unburned carbon.
What are the reagents to generate NO2+?
Concentrated sulfuric acid and concentrated nitric acid
What happens in the mechanism to generate NO2+?
Sulfuric acid donates a proton to nitric acid making H2NO3+ then another sulfuric acid donates another proton making H3O+ and NO2+ (and two lots of HSO4- are generated)
Why is nitration useful?
It's the first step of making TNT and amines, and amines are then used to make industrial dyes.
What is made in the combustion of TNT?
What is Friedel-Crafts acylation?
The reaction of an aromatic compound with [R-C=O]+ which is catalysed by AlCl3 (it's electrophilic substitution)
What is the name of (benzene)NH2
How are amines named?
Alphabetical order ending in -yl then amine e.g. methylpropylamine (apparently - I would check that because it says nothing about N- in the textbook)
What is the bond angle in ammonia and what is the bond angle in a perfect tetrahedron?
How can amines react?
As a base, when the N gains a H+ ion, and as a nucleophile, where the N donates the lone electron pair to an electron deficient carbon
What state are amines usually?
Very short chains are gases at room temperature, and slightly longer chains are volatile liquids. They also smell of rotting fish
What type of base is an amine?
If you react an alkylamine with hydrochloric acid, what's the resulting salt called?
Alkylammonium chloride (or sometimes alkylamine hydrochloride)
What is the inductive effect?
Where alkyl groups release electrons away from the alkyl group towards the positively charged atom (e.g. nitrogen atom acting as a base)
Explain the base strength of primary, secondary, tertiary and aryl amines.
Secondary are better than primary because there are 2 inductive effects happening but tertiary are not stronger than secondary because they are less soluble in water. Aryl groups are bad because they delocalise the lone pair of electrons into the benzene ring.
What happens to the smell of an amine when an acid is added?
It disappears because the involatile salt is formed.
What happens haloalkanes react with ammonia?
There's nucleophilic substitution of the halide by ammonia, and then by the primary amine produced, then by the secondary amine, then by the tertiary amine, and you end up with a quaternary ammonium salt.
How would you separate primary, secondary and tertiary amines?
How do you get mostly primary amine and less secondary amine and beyond?
Use excess of NH3
How can primary amines be made from haloalkanes in a two-step process?
Haloalkanes react with cyanide ion in aqueous ethanol - nucleophilic substitution. The resulting nitrile is then reduced to a primary amine by catalytic hydrogenation with a reducing agent e.g. LiAlH4 or Ni/H2 (but not NaBH4)
Why is reduction of nitriles preferable to reaction of ammonia with haloalkanes for making primary amines?
It produces a higher yield/purer product because only the primary amine can be formed.
How is phenylamine made from benzene?
Benzene and NO2+ make nitrobenzene. That is reduced to phenylamine using Sn/HCl but because there is hydrochloric acid the salt of the amine is formed so NaOH is added to make it normal phenylamine
What are amines used for?
Manufacture of nylon, polyurethane, dyes and drugs.
What are quaternary ammonium compounds used for?
Manufacture of hair and fabric conditioners due to the long hydrocarbon chain and positively charged organic group. Hair and fabric both pick up negative charges on their surfaces so the positive cations form a coating that prevents the build up of static electricity, keeping fabric smooth and preventing flyaway hair.
What on earth is a cationic surfactant
Quaternary ammonium compounds used in conditioner and stuff. In aqueous solution the ions cluster with the charged ends in the water and hydrocarbon tails on the surface.
What is an α amino acid? (Aka 2-amino acid)
One where the amino group is on the carbon next to the COOH
Which enantiomer occurs more in nature?
What is a zwitterion?
An amino acid with a permanent positive and negative charge, so NH4+ and COO-, and no overall charge.
What are the terms for gaining and losing an electron? (Not redox)
Protonated and deprotonated
What are some properties of amino acids?
Ionic, high melting points, dissolve well in water but poorly in non-polar solvents, white solid at room temperature.
What is the term for a compound with two functional groups?
What is the bond between amino acids called?
What is a molecule with up to about 50 amino acids called?
What is a molecule with more than 50 amino acids called?
Name some naturally occurring proteins
Enzymes, wool, hair, muscles
What is a peptide with two amino acids called?
What is another word for a peptide link between amino acids?
An Amide linkage (because it almost has the amide functional group thing, -CONH- instead of -CONH2)
What type of polymers are polypeptides?
Condensation, because water is eliminated for each link of the chain
How do you break a peptide?
Boil with 6 moldm-3 HCl for about 24 hours and you get all the amino acids separately
How do you separate and identify amino acids?
Chromatography (usually paper) and compare with known samples if you want to see if a particular amino acid is there
How can proteins be sequenced?
Certain enzymes partially hydrolyse specific proteins so will only break specific peptide bonds. Then there's a ton of complicated stuff that happens.
Why do proteins have complex shapes?
What's a shape of a protein apart from a helix?
Why are proteins biodegradable?
They can be hydrolysed
How do enzymes work, shape-wise?
They fit closely to the molecules that are reacting and hold them in the correct orientation to react
What's the thing called that an enzyme catalysts the reaction for?
The substrate of that enzyme.
What does changing temperature and pH do to enzymes?
Disrupts the hydrogen bonds so they denature. This means enzymes have an optimum temperature and pH
Why do you have to wash wool at a low temperature?
There are hydrogen bonds in the fibres which make it stretchy, but at high temperatures the hydrogen bonds break so the garment may permanently lose its shape.
Why are addition polymers (polyalkenes) not biodegradable?
They have strong non-polar C-C and C-H bonds so are very unreactive so can't be attacked by biological agents.
What is a polyester?
A condensation polymer with the ester linkage (-COO-) repeated. Made from diols and dicarboxylic acids alternating.
How can a polyamide be made apart from with amino acids?
Using a diaminoalkane and dicarboxylic acid
Name two useful polyamides
Nylon and Kevlar
What are the things that make Nylon-6,6?
1,6-diaminohexane and hexane-1,6-dicarboxylic acid (though that's industrially, in a lab the reaction is faster with a diacid chloride which means HCl is eliminated)
What does potassium dichromate do?
Acidified with dilute H2SO4, it oxidises primary and secondary alcohols, and aldehydes.
What is NaBH4 used for?
Reducing C=O but not C=C in aqueous solution. This is because it generates the H- nucleophile which attacks partially positive C but is repelled by the electron density around C=C
What is H2/Ni used for?
Reducing C=C but not C=O
What is Sn/H+ used for?
Reducing R-NO2 to R-NH2
How are alcohols converted to alkenes?
Passing their vapour over heated aluminium oxide, or by acid-catalysed elimination reactions.
What does acidity suggest about an organic molecule?
Acidic: carboxylic acid. Basic: amine
What does state at room temperature suggest about an organic molecule?
Solid: long chain or ionic. Liquid: medium chain or polar or hydrogen bonding. Gas: short chain, little or no polarity
What does solubility in water suggest about an organic compound?
Whether it has polar groups or not.
What does a smoky flame suggest about an organic compound?
High C:H ratio, possibly aromatic.
What do you get if you cross an acyl chloride with AgNO3?
A vigorous reaction. White precipitate of AgCl forms. That's the test for acyl chlorides apart from dropping water in and getting white misty fumes.
What are the ions formed in a mass spectrometer called?
Why might there be small peaks of greater mass than the molecular ion in the mass spectrum?
Isotopes such as 13-C mess stuff up. Don't worry about it.
What do you get when the molecular ion breaks up? What is detected?
A fragment with the positive charge and a fragment with the unpaired electron. The charged fragment is the one that is deflected in the mass spectrometer.
What's an acylium ion and why is it stable?
It's a RCO+ and the stability has something to do with the C=O idk the textbook kinda contradicts itself here. The positive charge is on the carbon anyway and carbons are usually cool with positive charges.
What's the M+1 peak on the mass spec?
The tiny peak with an m/z ratio one bigger than the molecular ion peak. It's the peak formed by the molecules where 1 carbon is carbon-13 not 12. Because 1% of carbon atoms are carbon-13, the % height of the M+1 peak compared to the molecular ion peak tells you how many carbons are in the compound, e.g. if the height is 4% of the main peak, there are 4 carbons.
What's special about chlorine in mass spec?
It has two isotopes, 35 and 37, in a ratio 3:1 so peaks with intensity ratio 3:1 two m/z values apart suggest the presence of chlorine.
What's special about bromine in mass spec?
Two isotopes 79 and 81 almost exactly in 1:1 abundance, so figure it out Alexander. That's an order from your commander.
What are the axes on an IR spectrum?
Transmission against wavenumber.
How does IR spec work?
Shine a beam of infra-red radiation through a sample, molecules absorb energy and bonds vibrate more. Absorb same frequency as natural vibrational frequency of bond. Radiation that emerges misses frequencies corresponding to bonds in the sample.
What is the fingerprint region of an IR spectrum?
The area below about 1500cm^-1 which has peaks caused by the vibrations of the whole molecule which is unique for any particular substance. Therefore it can be used to identify a substance by matching it to a computer database thingy
What is the standard in NMR spectroscopy and why is it good
TMS because all 4 carbons and 12 hydrogens are in exactly the same environment with lots of shielding so there's a single clear peak at the far right of the spectrum. It's also inert, non-toxic, and easy to remove from the sample.
What's splitting in proton NMR called?
What solvents can be used in H NMR and why?
They can't have H in so CCl4 for non-polar, CDCl3 or D2O for polar.
What's the weird disappearing peak thing in hydrogen NMR?
If a peak disappears in D2O it's probably on the OH of an alcohol because the H swaps with the D in the heavy water so disappears. It happens whenever a H can easily leave the molecule, so NH3 does it and probably some others too.
What is the mobile phase?
What carries the soluble components of the mixture. The more soluble the component is in the mobile phase, the faster it moves. The solvent in the mobile phase is often called the eluent (in column chromatography)
What is the stationary phase?
What holds back the components in the mixture which are attracted to it. The more affinity a component has for the stationary phase the slower it moves with the solvent.
Describe column chromatography
Statationary: powder e.g. silica, aluminium oxide, or a resin. Packed into narrow tube. Solvent (eluent) added at top and runs down column. Components collected separately in flask at bottom. Good because large amounts can be separated and collected.
What's an important thing to say in chromatography?
Components move at different rate. Have different retention times.
Describe gas-liquid chromatography
Stationary: powder coated with oil packed into/coated on inside of long capillary tube. (100m long, 1/2mm diameter)
Mobile: unreactive gas (nitrogen or helium)
Sample is carried along by gas and mixture separates as some of the components move along with the gas and some are retained by the oil, each to a different degree. Leave column at different times after injection. Different retention times. Various detectors.