chem paper 2

what are benefits of high atom economy

reduces production of unwanted products

makes process more sustainable

maximises profit

what are permanent dipole dipole forces

weak electrostatic forces of attraction between delta pos and delta neg charges on neighbouring moleucles 

activation energy

minimum amount of kinetic energy particles need to react

effect of increased temperature on reaction rate

molecules will have more kinetic energy and will move faster - greater proportion will have energy greater than or equal to the activation energy

rate of reaction

change in the amount of a reactant or product over time

effect of conc on reaction rate

particles will be closer together

collisions will be more frequent - more chances for particles to react

what is reaction order

power to which the concentration of that reactant is raised in the rate equation.

what is the rate constant

number that connects the concentration of reactants in a reaction to the rate of that reaction.

as activation energy increases, what happens to k

k gets smaller

arrhenius plots

lnk = yaxis

1/T = x axis

line of best fit = = -Ea/R

y intercept = lnA

increased no. particles means

higher rate of reaction

more particles within a given volume, so more successful collisions per unit time

having a higher surface area ..

more frequent sucessful collisions with surface of catlyst per unit time

Magnesium ribbon reacts with hot water. Heated magnesium ribbon reacts with steam. State two differences between these reactions

Slower with hot water or faster with steam The hot water produces Mg(OH)2

/ the hydroxide OR steam produces MgO / the oxide (Slow) bubbling with hot water OR bright white light / flame / white solid with steam

State le Chatelier’s principle.

(If any factor is changed which affects an equilibrium), the (position of) equilibrium will shift / move so as to oppose / counteract the change.

State how, if at all, the number of molecules with the most probable energy (Emp) changes as the temperature is decreased without changing the total number of molecules.

increases

why are initial concentrations used

(b) (At time zero/start) the concentrations are known

(a) Suggest why the order with respect to iodine is zero.

iodine is not in rate determining step

what is structural formula

shows the atoms carbon by carbon, with attached hydrogens and functional groups

general formula

algebraic formula that can describe any member of a family of compounds

what is a homologous series

family of compounds with same functional group and general formula

differ by CH2

chain isomers

same functional groups but different arrangements of the carbon skeleton

position isomers

same skeleton and same atoms or groups of atoms attached - but the atoms/groups of atoms are attached to diff carbon atoms

functional group isomers

same atoms arranged into diff functional groups

bond angles in alkenes

120

carbon neutral

no net emissions of carbon dioxide/CO2 to the atmosphere

cracking of alkanes involves

breaking C-C bonds

fractional distillation process

crude oil vaporised at 350C

goes thru bottom of column and rises (there is a temp gradient in the column)

largest hydrocarbons dont vaporise - as BPS too high

fractions drawn off at different levels

why crack hydrocarbons?

high demand for lighter fractions

overall reaction with ozone

2O3 → 3O2

nucleophile

electron pair donor

nucleophilic substitution conditions

OH- : use warm aqueous NaOH/KOH

CN: ethanolic + aqueous KCN (under reflux)

NH3: ethanolic NH3

elimination conditions

OH- ions dissolved in ethanol (warmed) under reflux

what is a base

proton acceptor

c=c bond has

high electron density

why are carbocations with more alkyl groups more stable?

alkyl group are electron releasing - so they stabilise the positive charge

what are plasticisers

plasticiser makes polymer bendier

• get between polymer chains and push them apart- reducing strength of IM forces between chains

dehydration conditions and mechanism

heat

conc sulfuric acid

why are addition polymers unreactive

saturated

non polar carbon chain

hydrating alkenes conditions

steam at 300C

high pressure

phosphoric acid catalyst

biofuel

fuel made from biological material that recently died

aldehyde to COOH eqaution

CHO + [O] → COOH

under reflux

primary alcohol to aldehyde

acidified potassium dichromate and distill

secondary alcohol to ketone

reflux

acidified potassium dichromate

testing for primary/secondary/tertiary alcohols

add 2cm3 acidified potassium dichromate

warm in hot water bath

orange to green

brick red precipitate

copper oxide

using mass spec, what can be determined

molecular formula

electrophilic additionn

in electrophilic addition, Br-Br bond becomes

polarised

what is a racemate

contains equal quantities of each enantiomer

they have no optical activity

50/50 mix of each enantiomer

reducing an aldehyde/ketone

RCHO + 2[H] → RCH2(OH)

RCOR +2[H] → RCH(OH)R

reagent to reduce C=O

aqueous NaBH4

KCN

toxic gas

We could use HCN for this reaction but it is a toxic gas that is difficult to contain. KCN/NaCN are still, however, toxic, because of the cyanide ion.

HCN is also a weak acid - partially ionises

esterification conditions

conc sulfuric acid catalyst

reflux

what are animal fats and vegetable oils

esters of glycerol and fatty acids

hydrolysis of fats and oils

heat with NaOH (alkaline conditions)

glycerol + sodium salt (soap)

to convert back to fatty acid add HCl

making biodiesel

fat/oil + methanol → (KOH catalyst) glycerol + methyl ester (biodiesel)

methyl esters of long chain fatty acids = biodiesel

how to make aspirin

ethanoic anhydride and the benzene molecule with OH and COOH

why ethanoic anhydride over ethanoyl chloride

less corrosive

cheaper

doesnt produce toxic HCl fumes

benzene structure

planar

bonds lengths same in all bonds (lies inbetween single and double bond length)

p orbital electrons delocalise and increase stability

why substitution instead of addition reactions in benzene

benzene ring so stable

addition reactions would destroy delocalised ring of electrons

to only substitute with one NO, what do u need to do

temp below 55C

conditions for friedel crafts acylation

• reflux

• ether

• acyl chloride

• AlCl3

what are cationic surfectants

partially soluble

insoluble in water

quaternary ammonium salts

• long hydrocarbon chain insoluble in water, will bind to non polar substances like grease; the positively charged ion is soluble in water

• - used in conditioners

how do amines act as weak bases

accept protons

theres a lone pair of electrons on the N atom that forms a coordinate bond with H+ ion

aliphatic amines - stronger bases

forming amines from nitriles

LiAlH4 in dry ether + dilute aci

nitrobenzene → phenylamine

sn + hcl

add alkali (naoh)

nylon 6,6

1,6 diaminohexane and hexanedioic acid

clothing/rope

kevlar

benzen-1,4 dicarboxylic acid and 1,4-diaminobenzene

bulletproof vests/car tyres

terylene

benzene- 1,4 dicarboxylic acid and ethane-1,2-diol

clothes/bottles

polyamides and polyesters hydrolysed more quickly in

acidic and basic conditions respectively

zwitterions only exist near..

isoelectric point - pH where overall charge on the amino acid is zero

to break up proteins

reflux with HCL for 24 hours

describe disulphide bonding

amino acids part of protein - called residue

disulphide bonds occur between residues of the amino acid cysteine

how does cisplatin work

nitrogen atom on guanine base in DNA forms coordinate bond to platinum ion, replacing a chlorine ligand

• prevents strands unwinding - so dna cant be replicated

TLC

plate coated with solid and solvent moves up plate

CC

solid packed in and solvent moves down column

• used for purifying organic products

GC

for mix of volatile liquids

solid or solid coated by liquid and a gas

under pressure + at high temp

how does CO2 cause global warming

C=O Bonds in CO2 absorb infrared radiation (of 2350 cm–1 ) 1 IR radiation emitted by the earth does not escape (from the atmosphere)

conditions for basic ester hydrolysis

aqueous warm NaOH

bonding in benzene

1a) Each C has three (covalent) bonds 1b) Spare electrons (in a p orbital) overlap (to form a π cloud) 1c) delocalisation

why use two solvents in chromatography

Some of the amino acids did not separate/dissolve with the first/either solvent OR Some amino acids have the same Rf value or have the same affinity with the first/either solvent

disappearing cross graph

1/T = rate

plot rate (y axis) against T (x axis)

sketch plot

give practical reasons why the vol of gas is lower

hydrogen is lost before the syringe is connected

arrhenius graph axis

1/T on X axis

lnk on Y axis

benefits of using buchner flask to filter

filtration quicker, product drier

obtaining pure sample + crystalising method

why reflux?

explain process

allows reactant vapours to return to the organic mixture

heated to boiling point for a prolonged period of time

vapour is formed which escapes from the liquid mixture, is changed back to liquid and returned to liquid mixture

any mixture that initially evaporates can then be oxidised

why cool distillate

to reduce evaporation

when distilling a mixture - to obtain one of the liquids, how should the boiling temp be adjusted

boil ate boiling point of liquid u want

what does having different polarities of amino acids mean for amino acids having diff rfs

diff relative retention on stationary phase

why are acid strength of ethanedioic acid and ethanoic acid different

Stage 1: difference in structure of the two acids • The acids are of the form RCOOH • but in ethanoic acid R = CH3 • whilst in ethanedioic acid R = COOH

Stage 2: the inductive effect • The unionised COOH group contains two very electronegative oxygen atoms • therefore has a negative inductive (electron withdrawing) effect • The CH3 group has a positive inductive (electron pushing) effect

Stage 3: how the polarity of OH affects acid strength • The O–H bond in the ethanedioic acid is more polarised / H becomes more δ+ • More dissociation into H+ ions • Ethanedioic acid is stronger than ethanoic acid

ethanedioic acid + potassium manganate

5H2C2O4 + 16H+ + 2MnO4- → 2Mn2+ + 10CO2 + 8H2O

increasing the pressure of rate equation reaction by x3 - what happens to overall rate (two 1st order reactants)

increases by factor of 9

sodium carbonate + gallium II nitrate

gallium(III) hydroxide + CO2 forms

Explain qualitatively why doubling the temperature has a much greater effect on the rate of the reaction than doubling the concentration of E.

Reaction occurs when molecules have E>Ea

Doubling T by 10 °C causes many more molecules to have this E

Whereas doubling [E] only doubles the number with this E

how does the graph show that the order is zero

gradient constant

as conc decreases

 A general equation for a reaction is shown. 

A(aq) + B(aq) + C(aq) → D(aq) + E(aq) 

In aqueous solution, A, B, C and D are all colourless but E is dark blue. 

A reagent (X) is available that reacts rapidly with E. This means that, if a small amount of X is included in the initial reaction mixture, it will react with any E produced until all of the X has been used up. 

Explain, giving brief experimental details, how you could use a series of experiments to determine the order of this reaction with respect to A. In each experiment you should obtain a measure of the initial rate of reaction

The following rate equation was deduced. 

rate = k [CH₃COCH₃][H⁺] 

(a)     Suggest why the order with respect to iodine is zero. 

iodine isnt in rate determining step

molecular formula of glycerol

HOCH₂CH(OH)CH₂OH