Chemistry A2 Paper 5
Explain the reasons for the difference in basicity between ammonia, primary aliphatics amines (straight chain) and primary aromatic amines (Benzene ring)
(CH3 attatched to the NH2) CH3 is an electron donating side group, causing an indictive effect Lone pair is now more readily avaliable The electrons in the p orbital on the N interact with the negative ring on the benzene Lone pair on the nitrogen is less readily avaliable
Amines complex ion formation with copper (II)
(Cu(CH3NH2)4)4(H2O)2)2+ (Cu(H2NCH2NH2)3)2+ Deep blue solution
Equations to represent how ligand exchange can lead to a change in color (Cu + Co)
(Cu(H2O)6)2+ + 4Cl- > (CuCl4)2- + 6H2O (Yellow Tetrahedral) (Co(H2O)6)2+ + 4Cl- > (CoCl4)2- + 6H2O (Blue Tetrahedral)
Equation demonstrating the Chelate effect
(Cu(H2O)6)2+ + EDTA4- > (Cu(EDTA))2- + 6H2O (2 moles to 7 moles > Large Entropy change)
Tetrahedral
(CuCl4)2- 109.5 bond angle
Deprotonation (M = metal)
(M(H2O)6)2+ + 2OH-(aq) > M(H2O)4(OH)2(s) + 2H2O(l) (M(H2O)6)3+ +3OH-(aq) > M(H2O)3(OH)3(s) + 3H3O(l)
As TiCl3 is blue and TiO2+ ions are colourless in aqueous solution, the titration can be carried out without an alizarin indicator. Assess the teacher´s statement.
(Ti(H2O)6)3+ partially filled d-subshell splitting in energy of d-subshell by water/ligands Absorbtion of light/photon AND electronic transition color due to reflected/transmitted light Clearer color change at end point with indicator
Test for carbonyl group
2,4 - dinitrophenyl - hydrazine (Brady's reagent) Warm > orange ppt
What standard conditions are required for SHE?
298K + 1 M HCl Pressure of all gases = 1 atm Concentration of all solution = 1 mol dm^-3
Explain using an equation how a catalytic converter decreases amounts of carbon monoxide and nitrogen monoxide from emissions?
2CO(g) + 2NO(g) (reversible rxn) N2(g) + 2CO2(g) Nitrogen monoxide is absorbed onto the surface of the catalyst. This weakens the N=O bond. When carbon monoxide collides with the NO, CO2 is produced as well as nitrogen Nitrogen will desorb from the surface
Interconversion of dichromate (VI) ion to chromate (VI) ion
2CrO42-(aq) + 2H+(aq) (reversible rxn) Cr2O72-(aq) + H2O(l) (Yellow to orange) Add H+ increases (H+) push equilibrium to the right so more orange Add NaOH OH- neutralises H+ (H+ decreases) pushes equilibrium to the left so more yellow
What catalyst is used in the reaction between Iodide and Thiosulphate? What type of catalyst is it? Use equations to explain its function
2I- + S2O82- > 2SO42- + I2 Fe2+ or Fe3+ 2Fe3+(aq) + 2I-(aq) > 2Fe2+(aq) + I2(aq) 2Fe2+ + S2O82- > 2SO42- + 2Fe3+ (Reactions 1 or 2 can occur in either order)
Catalyst used in the Contact Process. Use equations to demonstrate how it works? Vanadium (V) Oxide (V2O5)
2SO2(g) + O2(g) (reversible rxn) 2SO3(g) V2O5 + SO2 > SO3 + V2O4 2V2O4 + O2 > 2V2O5
Explain why the solution of copper (II) sulfate dissolving in water would be colored to form a blue solution
3d orbitals split Electrons are promoted (from lower to higher energy d orbitals) Absorbing energy/photons of a certain frequency Reflected/transmitted light is colored/in the visible region
Equation for the reduction of 4-nitro-phenol
4 nitrophenol > 4-hydroxyphenylamine (conc HCl + Tin) (Draw them out)
Conversion of alcohol to bromoalkane
50% concentrated H2SO4 + KBr Warm
Reaction of concentrated nitric acid and concentrated sulphuric acid with benzene
50-60C Too low = reaction too slow Too high = further substitution H2SO4 + HNO3 > HSO4- + H2NO3+ H2NO3+ > H2O + NO2+ (Electrophile) Benzene + NO2+ > Benzene - NO2 + H+
Reaction of fuming concentrated sulfuric acid with benzene
50C SO3 dissolved in concentrated H2SO4 Benzene + HSO3+ > Benzene - SO3H + H+
Methanol fuel cell: Cathode
6H+ + 6e- + 3/2O2 > 3H2O
Which is true of the hydrogen - oxygen fuel cell? A The cathode has a more positive potential than the anode B Hydrogen is oxidised at the cathode C Oxygen is reduced at the negative electrode D The cell potential is different when operating under alkaline or acidic conditions
A
Which type of compound cannot be a monomer in the formation of polyamides? A amides B amino acids C diacyl chlorides D diamines
A
Transition metal
A d block element that has 1 or more stable ions with a partially filled d subshell
Sometimes the calculated E cell for a reaction shows it to be thermodynamically feasible but in a laboratory no reaction occurs. Give two possible explanations for this.
A high activation energy is high Conditions of the reaction are not standard Temperature not 298K Reaction is slow Reaction is kinetically unfavourable
Hexadentate: EDTA4-
A special ligand that forms 6 dative covalent bonds
Hydrogen - oxygen fuel cell (Advantages and disadvantages)
A: Alternative to fossil fuels No CO2/CO/oxides of nitrogen as products Lighter + more efficient than fossil fuels D: Compressing gas > hazardous Hydrogen explodes easily when ignited so great care in transportation Metal hydrides absorb hydrogen, requiring a high temperature to release H Produced from CH4 > finite resource
Amphoteric Behaviour
Ability of a substance to react with both acids and bases
Conversion of 2 alcohol to ketone
Acidified K2Cr2O7 Heat under reflux
Conversion of 1 alcohol to aldehyde
Acidified K2Cr2O7 Heat/Distillation
Frield-Crafts acylation of benzene
Acyl + AlCl3 Dry RT
Acidity, Basicity and formation of Zwitterion
Add Acid NH3+ Add Alkali -OOC + H2O At a specific pH BOTH -OOC and NH3+ Crystaline ionic solid
Test for Halogenoalkane
Add NaOH warm Acidified silver nitrate Cl > white ppt > redissolves in dilute NH3 Br > cream > redissolves in conc NH3 I > yellow
Test for alkene
Add bromine water Orange to colorless
Write an equation to show the formation of poly(ethanol)
Addition polymerisation (Ref to notes)
Draw the mechanism for the reaction between benzene and halogens (ELECTROPHILIC SUBSTITUTION)
AlBr3 + Br2 > AlBr4- + Br+ Ring system breaking > draw AlBr4- + H+ > AlBr3 + HBr
Conversion of acyl chloride to ester
Alcohol RT
Conversion of carboxylic to ester
Alcohol + conc H2SO4 Warm
Test for C=O-CH3 or C-OH-CH3-H
Alkaline solution of Iodine (Oxidises 2 alcohol) > yellow ppt
Reaction of Friedel-Crafts
Alkylation (AlCl3) CH3Cl + AlCl3 > AlCl4- + CH3+ (Electrophile) Benzene + CH3+ > Benzene - CH3 + H+ (methylbenzene) Acylation (AlCl3) CH3COCl + AClCl3 > AlCl4- + CH3CO+ (Electrophile) Benzene + CH3CO+ > Benzene - C=O - CH3 (phenylethanone)
Write an equation to show the formation of proteins
Amino acids but repeated Condensation polymerisation
Difference in color between anhydrous and hydrated copper (II) sulphate
Anhydrous = white Hydrated = blue
Which organic compound reacts with a Grignard reagent to give a product that forms a secondary alcohol on hydrolysis? A carbon dioxide B ethanal C methanal D propanone
B
Which of the following statements BEST explains carbon monoxide poisoning? A carbon monoxide binds irreversibly to haemoglobin B carbon monoxide forms stronger dative covalent bonds with hb than oxygen does C the formation of carboxyhaemoglobin leads to a large increase in the entropy of the system D carbon monoxide has a triple bond whereas oxygen has a double bond
B (B explains why A happens)
Phenol
Benzene ring with -OH
Use the reaction between phenol and brome water to demonstrate the activation of the benzene ring
Benzene will not react with Br2 water Phenol reacts at r.t + no catalyst often forming a trisubstituted ring system Lone pair of electrons in p orbital of oxygen interacts with the negative ring system (Delocalised with the ring of electrons) Increases electron denisty, for an easier reaction (Phenol + 3Br2(aq) > 2,4,6 - tribromophenol)
Transition metals, their compounds and their ions can act as heterogenous and homogenous catalysts. Compare and contrast these two types of catalytic behaviour Include one specific example from transition metal chemistry of each of these types of catalyst and a reaction in which it is used.
Both catalsys increase the rate of reaction by providing an alternative route with a lower Ea A heterogenous catalsy is in a different phase from the reactants and a homogenous catalyst is in the same phase Heterogenous: Iron in Haber Process Homogenous: Iron (II)/Iron (III) ions and reaction btw iodide ions and persulfate ions Heterogenous works by the reactant molecules absorbing onto the catalyst surface, where bonds are weakened, and the reaction takes place then product molecules desorb Homogenous works by the transition metal being oxidised to a different oxidation state then changing back to the original oxidation state.
Bromine reacts with cyclohexene to form 1,2 - dibromocyclohexane, and with benzene to form bromobenzene. Compare and contrast these reactions, considering the type and mechanism of each reaction and the conditions required.
Both reactions involve electrophilic attack Both reactions form a carbocation Reaction with benzene is substitution because the benzene ring is restored Reaction with cyclohexene is addition because sigma bonds stronger than pi bonds Reaction with benzene requires a catalyst and heat AND whereas reaction with cyclohexene occurs under normal laboratory conditions
Bromination of benzene
Br2 (l) + AlBr3 Dry RT
Test for phenol
Bromine water Orange to colorless White ppt
The value for E cell for a reaction is positive. It can be deduced that the A entropy change for the system must be positive B entropy change for the surroundings must be positive C total entropy change must be positive D entropy change for the system and the entropy change for the surroundings must both be positive
C
Molecular formula benzene
C6H6
Demonstrate an understanding of the functional group of an amine including several examples
CH3CH2CH2 (-N:H2) Ethylamine Phenylamine (6C - NH2) N - methyl ethylamine (N > tells us the groups on the N) CH3CH2NHCH3
Draw the mechanism for the reaction between benzene and a halogenoalkane including the formation of the electrophile
CH3CH2Cl + AlCl3 > AlCl4- + CH3CH2+ Ring system breaks (Electron) AlCl4- + H+ > AlCl3 + HCl
Synthesis of Amides: Write an equation to demonstrate how amides are formed from acyl chlorides
CH3COCl + CH3NH2 > CH3CONHCH3 + HCl (N-methylethanamide)
Amines treatment with ethanoyl chloride
CH3NH2 (Lone pair ON N) + CH3COCl (dipole) > CH3CONHCH3 + HCl (N-methylethanamide)
Amines reaction with halogenoalkanes
CH3NH2 (Lone pair ON N) + CH3Cl > CH3NH2CH3 (+ ON N) + Cl- > CH3NHCH3 (Lone pair ON N) + HCl Excess of CH3NH2 will limit further substitution > major product = 2nd amine Excess of CH3Cl it will lead to further oxidation > (CH3)3NH > (CH3)4N+
Overall equation for methanol-oxygen fuel cell
CH3OH + 3/2O2 > 2H2O + CO2
Methanol fuel cell: Anode
CH3OH + H2O > CO2 + 6e- + 6H+
Explain the role of the transition metal in hb? What issues arise from carbon monoxide
CO binds irreversibly to Hb, reducing the blood´s capacity to carry oxygen
Reduction of aromatic nitro compounds
Can be reduced to amines by use of Tin and concentrated HCl acid Lithium aluminium hydride will reduce the nitro group to a zo product
Acute toxicity
Can cause life threatening effects in small quantities
Comment on the solubility of poly(ethenol) and its use in liquitabs?
Can form many hydrogen bonds with water Used to make soluble plastics for detergents or hospital laundry bags
Heterogenous catalyst
Catalysts are in a different phase Pt, V2O5 (Contact), Fe (Haber)
Homogenous catalyst
Catalysts are in the same phase Fe2+/Fe3+
Flammable
Catched fire when heated or in contact with a flame
Complex
Central metal atom or ion surrounded by ligands
Give a possible reason why the chloro complexes of iron ions have a coordination number of four rather than six.
Chloride ions are large so steric hinderance is too great for six ligands to coordinate around the central ion
When Cr(III) is converted to Cr(II) in aq solution, air has to be kept out of the aparatus. Explain why this is necesary.
Chromium (II) is readily oxidised back to Chromium (III) by oxygen (in the air)
Discuss the use of platinum complexes in the treatment of cancer?
Cis platin (Trans so it shows geometric isomerism) Prevents cancer cells from replicating (inhibits DNA strands from separating) However it also stops non cancer cells from replicating so can have side effects such as hair loss
Square planar
Cis platin chemotherapy drug 90 bond angle
Cu2+ (colors)
Color of agua ion: Blue solution Addition of droplets of NaOH: Blue ppt Addition of droplets of NH3: Blue ppt Addition of excess NH3: Redissolves to form a deep blue solution Addition of NaOH: Does not resdissolve
Zn2+ (colors)
Color of agua ion: Colorless Addition of droplets of NaOH: White ppt Addition of excess NaOH: Redissolves to form a colorless solution Addition of droplets of NH3: White ppt Addition of excess NH3: Redissolves to form a colorless solution
Cr3+ (colors)
Color of agua ion: Green Addition of droplets of NaOH: Green ppt Addition of excess NaOH: Ppt redissolves to form a green solution Addition of droplets of NH3: Green ppt Addition of excess NH3: Ppt redissolves to form a violet
Ni2+ (colors)
Color of agua ion: Green solution Addition of droplets of NaOH: Green ppt Addition of droplets of NH3: Green ppt Addition of excess NH3: Redissolves to form a deep blue solution Addition of NaOH: Does not resdissolve
Fe2+ (colors)
Color of agua ion: Pale green solution Addition of droplets of NaOH: Green ppt turns brown in air Addition of droplets of NH3: Green ppt turns brown in air Addition of excess NaOH/Excess NH3: Does not redissolve
Mn2+ (colors)
Color of agua ion: Pale pink Addition of droplets of NaOH: Pale brown ppt that darkens in air Addition of droplets of NH3: Pale brown ppt that darkens in air Addition of excess NaOH/Excess NH3: Does not redissolve
Co2+ (colors)
Color of agua ion: Ruby red solution Addition of droplets of NaOH: Deep blue ppt turns pink in air Addition of droplets of NH3: Deep blue ppt turns pink in air Addition of excess NH3: Redissolves to form a pale yellow solution (brown in air) Addition of NaOH: Does not resdissolve
Fe3+ (colors)
Color of agua ion: Yellow brown solution Addition of droplets of NaOH: Brown ppt Addition of droplets of NH3: Brown ppt Addition of excess NaOH/Excess NH3: Does not redissolve
End point of titration with potassium manganate solution (VII) solution
Colorless to pale pink
Nitration of benzene
Conc HNO3 + conc H2SO4 50-60C
Reagents and conditions needed to convert benzene to nitrobenzene.
Concentrated nitric acid and concentrated sulfuric acid 55C
Polymerisation
Condensation Functional groups such as carboxylic acid, acyl chloride with alcohol or amine. Small product of water or HCl produced. Addition Alkenes and a SINGLE product
Electrochemical cell
Connecting 2 half cells (1 side oxidation and 1 side reduction > redox reaction)
Explain how stable iron (III) ions can be formed from iron (II) ions in aqueous solution. Refer to the relevant energy changes of these ions only.
Conversion of Fe2+ to Fe3+ requires large amounts of energy/is very endothermic The energy is recovered hydration (which is exothermic) The hydration of Fe3+ is more exothermic than Fe2+ and because the Fe3+ has a greater charge
Deprotonation (M = metal) Excess of OH- (Ligand Exchange = redissolve)
Cr(H2O)3(OH)3 + 3OH-(aq) > (Cr(OH)6)3- + H2O Zn(H2O)4(OH)2(s) + 2OH-(aq) > (Zn(H2O)2(OH)4)2- + 2H2O(l)
Amphoteric Behaviour of Chromium (Cr)
Cr(H2O)3(OH)3(s) + 3OH-(aq) > (Cr(OH)6)3- + 3H2O Cr(H2O)3(OH)3(s) + 3H+(aq) > (Cr(H2O)6)3+
Reactions of metals of Cr Co2+ + Ni2+ (M) Cu2+ Zn2+ with excess NH3 (better ligand)
Cr(H2O)3(OH)3(s) + 6NH3(aq) > (Cr(NH3)6)3+ + 3H2O + 3OH- M(H2O)4(OH)2(s) + 6NH3(aq) > (M(NH3)6)2+ + 4H2O + 2OH- Cu(H2O)4(OH)2(s) + 4NH3(aq) > (Cu(H2O)2(NH3)4)2+ + 2H2O + 2OH- Zn(H2O)4(OH)2(s) + 4NH3(aq) > (Zn(NH3)4)2+ + 4H2O + 2H2O (H+ taken off until the substance becomes neutral, once neutral it cannot dissolve so precipitate forms because it is no longer polar)
Suggest why the (Cr(H2O)6)6+ ion does not exist
Cr6+ ion is small and highly charged so it is very polarising causing the OH bonds to be broken
Anydrous copper (II) sulphate is a white crystalline solid which dissolves in water to form a solution that has a pale blue color. Explain fully why it becomes colored when it is dissolved in water.
Cu2+ ions are surrounded by water ligands (3) d orbitals split Electrons absorb energy of a certain frequency Electrons are promoted (from lower to higher energy d orbital(s)) Reflected/transmitted/remaining light is colored/in the visible region
Which piece of apparatus normally used in solvent extraction? A Buchner funnel B Evaporating bath C Liebig condenser D Separating funnel
D
Which of the following species will not act as a ligand in the formation of a complex ion? A CH3NH2 B CN- C NH3 D NH4+
D (NO LONE PAIR)
Explain why a solution of Zn2+ is colorless?
Despite a splitting in energy of the d orbitals, Zn2+ does not have an unpaired electron so there is no room for the electron to be promoted
Using relevant Electrode potentials explain how the dichromate ion can be reduced to Cr3+ and Cr2+ by sinz in acidic conditions?
Dichromate on left side Compare it to Zn (on left) Equation for Cr3+ and Zn (Both on left) Orange to green to blue
Explain why solutions of Chromium (II) and Chromium (III) have different colors
Different energy gap between the (3)d obritals Because the different charge/oxidation state so different frequencies/energy are absorbed/reflected/transmitted
Demonstrate an understanding of the functional group in an amino acid including several examples?
Draw an amino acid (Most amino acids will have optical isomers) Glycine (R > H) Alanine (R > CH
Equation to calculate the energy of light absorbed
E = hf
Sc
Electron configuration of element: (Ar) 3d1 4s2 Electron configuration of simplest ion (Sc3+): (Ar) (NOT TRANSITION METAL) (21)
Cu (IMPORTANT)
Electron configuration of element: (Ar) 3d10 4s1 Electron configuration of simplest ion (Cu2+): (Ar) 3d9 (29)
Zn
Electron configuration of element: (Ar) 3d10 4s2 Electron configuration of simplet ion (Zn2+): (Ar) 3d10 (NOT A TRANSITION METAL) (30)
Ti
Electron configuration of element: (Ar) 3d2 4s2 Electron configuration of simplest ion (Ti2+): (Ar) 3d2 (22)
V
Electron configuration of element: (Ar) 3d3 4s2 Electron configuration of simplest ion (V2+): (Ar) 3d3 (23)
Cr (IMPORTANT)
Electron configuration of element: (Ar) 3d5 4s1 Electron configuration of simplest ion (Cr3+): (Ar) 3d3 (24)
Mn
Electron configuration of element: (Ar) 3d5 4s2 Electron configuration of simplest ion (Mn2+): (Ar) 3d5 (25)
Fe
Electron configuration of element: (Ar) 3d6 4s2 Electron configuration of simplest ion (Fe2+): (Ar) 3d6 (26)
Co
Electron configuration of element: (Ar) 3d7 4s2 Electron configuration of simplest ion (Co2+): (Ar) 3d7 (27)
Ni
Electron configuration: (28) (Ar) 3d8 4s2 Electron configuration of ion: (Ni2+) (Ar) 3d8
Assess the thermodynamic feasibility of preparing mangante (VI) by reacting manganate (VII) and manganese (IV) oxide in alkaline conditions.
Equation (2MnO4- + MnO2 + 4OH- > 3MnO42- + 2H2O) E cell = -0.3 E cell is very small Reaction may be shifted in the required direction using concentrated alkali
Compare the use of ethanoic acid and ethanoyl chloride in the reaction of 2-hydroxybenzanoic acid. State the suitability, any advantages and disadvantages of each.
Ethanoic acid does not react with phenol OH groups to form esters Reaction with ethanoic acid would be an equilibrium/reversible/not go to completion Reaction of ethanoic acid is slow/needs a catalyst/requires heat By-product is TOXIC HCl
How can the dichromate ion be produced from Cr3+? (Dissolve in water)
Excess Alkali (Cr(H2O)6)3+ + 6OH-(aq) > (Cr(OH)6)3-(aq) + 6H2O(l) Hydrogen Peroxide (Cr(OH)6)3- + 3H2O2(aq) > 2CrO42- + 8H2O + 2OH- Chromate (VI) Dilute Acid 2CrO42-(aq) + 2H+ (reversible rxn) Cr2O72-(aq) + H2O(l) Dichromate (VI)
Health hazard
Eye damage, rash, harmful if ingested (HCl is corrosive)
Give some examples of transition metals and their uses as industrial catalysts
Fe = Haber process V2O5 = Contact process Ni = Hydrogenation of Margarine Rd/Pd = Catalytic Connectors
Salt bridge
Filter paper w/saturated KNO3 solution Ions flow through which balances the charges
Monodenate: H2O, NH3, OH-
Form 1 dative covalent bond per ligand Small ligand > forms octahedral complexes
Monodenate: Cl-
Forms 1 dative covalent bond per ligand Large ligand: Often forms tetrahedral/square planar (NOT ALWAYS)
Transiton elements
Forms at least one ION with a partially filled/incomplete d-subshell
Sulfonation of benzene
Fuming conc H2SO4 40C
State the color change you would see when Cr(III) is converted to Cr(II) in the aq solution
Green to blue
Draw the mechanism for the reaction between benzene during nitration, including the formation of the electrophile?
H2SO4 + HNO3 > HSO4- + H2NO2 H2NO2 > H2O + NO2+ Ring system breaks (Electron)
Why is a solution of K2Cr2O7 BEST acidified with H2SO4?
H2SO4 cannot be oxidised
Conversion of aldehyde or ketone 2-hydroxynitrile
HCN/KCN 10-20C
Conversion of alkene to halogenoalkane (g)
HX > gaseous
What are the various ways of increasing the length of the carbon chain?
Halogenoalkane or carbonyl reacting with :CN- Friedel - Crafts (BENZENE) Grignard´s Reagent (Ref Notes)
Explain two different ways in which primary aliphatic amines can be prepared
Halogenoalkanes + Excess NH3 Reduction of Nitriles (LiAlH4 in dry ether) (Draw mechanisms)
Write an equation to show the formation of nylon
Hexa - 1,6 - dicarboxylic acid + Hexa - 1,6 - diamine > Nylon 6,6 (Condensation polymerisation)
Octahedral
Hexagua copper (II) ion 90 bond angle
The Kolbe-Schmitt process is carried out at 125 and high pressure. State how, if at all, these conditions for electrophilic substitution would have to change if this process was carried out with benzene in the place of phenol. Fully justify your answer in terms of the reactivity of benzene and phenol.
Higher temperature/pressure Phenol reacts with electrophiles much faster Phenol more reactive than benzene/reacts faster than benzene Because the electron density of the benzene ring in phenol is higher Due to interaction between the lone pair and the electrons of the benzene ring
Write an equation to show the formation of poly(propanamide)?
Highly absorbant of water (Ref notes)
Activation of Benzene
Increases the electron density of the benzene ring so it will react more readily by the addition of electron donating groups Does not NEED to be activated to react
Explain why a reference electrode is needed to measure the electrode potentials of chemical systems.
It is not possible to measure the potential difference between the metal electrode and ion solution.
Conversion of halogenoalkane to nitrile
KCN (ethanolic) Heat under reflux
Conversion of aldehyde to 1 alcohol Ketone to 2 alcohol Carboxylic acid to 1 alcohol Nitrile to primary amine
LiAlH4 Dry ether
Why are transition metals colored?
Ligands interact with some of the d-orbitals causing a splitting in energy of the orbitals Must be an unpaired d-electron Absorption of light promotes an electron from a lower to a higher energy level (electronic transition) Color observed is due to any unreflected light
Bidenate
Ligands that form 2 dative covalent bonds with the central cation Ethandioate ion (C2O42-) + Diaminoethane 3 bidentate ligands = optical isomerism
What factors can affect the size of the energy absorbed and therefore the color of the compound or ion?
Metal ions Charges Ligands Shape Coordination number (Stronger ligands lead to larger energy divides, more likely to absorb high energy violet and blue and so will red, yellow and orange)
Ligand
Molecule or ion that forms a dative covalent bond with a transition metal by donating a pair of electrons
Conversion of acyl chloride to primary amide
NH3 RT
Conversion of halogenoalkane to amine
NH3 (ethanolic) Heat under pressure
Write an equation to demonstrate the formation of dyes from aromatic compounds
NaNO2 + HCl > HNO2 + NaCl 0-10C or else the benzenediazonium ion will decompose Phenol + HNO2 > Benzenediazonium ion Final part of reaction (Draw as it is too complicated for the flashcard)
Conversion of halogenoalkane to alcohol
NaOH(aq) Heat under reflux
Hydrogen - oxygen fuel cell (Alkaline electrolyte)
Negative: H2(g) + 2OH-(aq) > 2H2O(l) + 2e- Positive: 1/2O2(g) + H2O(l) + 2e- > 2OH-(aq)
Hydrogen - oxygen fuel cell (Acidic electrode)
Negative: H2(g) > 2H+(aq) + 2e- Positive: 1/2O2(g) + 2H+(aq) + 2e- > H2O(l)
Phenylamine reacts rapidly with dilute sulfuric acid. The reaction is ?
Neutralisation
Co-coordination number
Number of covalent bonds to the central metal atom or ion
Half cells
One half an an electrochcemical cell Metal dipped in its ions (Platimun Electrode with 2 aq ions)
Anode
Oxidation takes place: Loss of e- Hydrogen undergoes: H2 > 2H+ + 2e- Electrons go into the metal of the anode, aquiring negative charge
Cathode
Oxygen is reduced and reacts with water to form hydroxide ion O2 + H2O + 4e- > 4OH- e- comes out of the cathode, aquirring a positive charge (If anode + cathode are connected, e- flow from the anode to the cathode allowing reactions to continue)
Conversion of alcohol to chloroalkane
PCl5 RT
Test for hydroxy group
PCl5 > Misty fumes Na > Effervesence
Explain in terms of electron configurations, why Fe2+ ions are readily oxidised to Fe3+ ions Mn2+ ions are not readily oxidised to Mn3+ ions
Paired electron in the full obrital in (3d in) Fe2+ is easily removed due to repulsion But the (3)d5 arrangement/half filled (3)d-subshell/half filled (3)d orbitals in Mn2+ is stable
NMR
Peaks > Environments Integration ratio > Number of Hs in each environment Splitting pattern > Hs on the adjacent C atoms (n+1 rule) Chemical shift > Functional groups
Use the reaction between phenol and dilute nitric acid to demonstrate the activation of the benzene ring?
Phenol + HNO3 (dilute) > 2-nitrophenol or 4-nitrophenol (Less than 10C) Pheno + 3HNO3 (concentrated) > 2,4,6 - trinitrophenol (Pictic Acid)
Phenol also has a delocalised structure. Compare the conditions and the products of the reaction for the bromination of phenol and benzene.
Phenol forms tribromophenol at room temperature with bromine water Benzene forms C6G5Br/Bromobenzene requiring a catalyst of Iron/Iron (III) bromide/ a halogen carrier
Suggest why platinum is used as the electrode and why it is coated in platinum black.
Platinum is chemically inert and using Pt black increases the surface area, making catalysis more effective
Grignards Reagent
R-Br + Mg > R-Mg-Br (H+, H2O) CO2 > RCOOH CH3OH > RCH2OH RCOH > secondary RCOR > tertiary
Conversion of acyl chloride to secondary amide
R-NH2 (Amine) RT
Frield-Crafts alkylation of benzene
R-X + AlX3 catalyst Dry RT
Formation of peptide groups in proteins
Reaction of a -NH2 group in one amino acid with a -COOH on another Peptide link/bond
Halogenoalkane/carbonyl reacting with :CN- (Increasing the length of the carbon chain)
Reagents KCN + Hydrogen cyanide R-X > R-C(triple)N > R-CH2-NH2 R-C=O-R´ > R-C-CN-OH-R´
Conversion of alcohol to iodoalkane
Red phosphorous + I2 Heat under reflux
EMF equation
Reduced - oxidised
Explain why benzene is resistant to bromination, compared to other alkenes?
Ring system provides far greater stability and therefore is more difficult to break than solitary discrete pi bond in an alkane (Benzene ring system > very difficult to react It will reform. Slow reaction. Electrophile MUST be made)
Effect of aqueous solutions on plane-polarised monochromatic light
Shine plane polarised monochromatic light through a solution of a given amino acid Almost all amino acids have optical isomers so will rotate in the light in one direction If the amino acids are synthesized in a lab, they are likely to be a racemic mixture
Corrosive
Skin burns or permenant eye damage
Ionisation energies in transition metals
Small increase between the 2nd and 3rd (EXCEPT Cu and Cr) electron being removed > slightly significant jump (4s2 3d1 > first two easy where third is hard) A large increase in energy signifies that an electron has been removed from an inner shell (lower quantum energy level)
Conversion of nitrobenzene to phenylamine
Sn + concentrated HCl Heat under reflux
Test for carboxylic acids
Sodium carbonate Effervesence Gas given off turns limewater cloudy
SHE
Standard hydrogen electrode
Deprotonation
Strong covalent bond between positive metal ion and oxygen in a water ligand the oxygen-hydrogen bond is weakened. On the addition of a small amount of an alkali the hydrogen can be removed, resulting in a complex being formed that has a neutral charge overall. Complex no longer soluble and is a precipitate.
Explain the temperature should be neither higher nor lower than 5C in the reaction with the diazonium ion.
Temperature higher than 5C diazonium decomposes Temperature lower than 5C reaction too slow
Comment on the physical properties of polyamides
Tend to be crystaline > strong attractions between the chains Used in fibers > due to the strong bonds in the amide group
Write an equation to show the formation of Kevlar
Tetrapthalic acid + Benzene - 1,4 - diamine > Kevlar Many inter chain bonds so high tensile strength Additional strength from aromatic stacking
Describe the delocalised model
The 6 p orbitals of the carbon atoms overlap colectively to form a ring of negative charge above and below the plane of the molecule
Explain, in terms of electronic structure, why iron (III) compounds are more stable than iron (II) compounds
The electronic structure of Fe(II) (Ar)3d6 and Fe(III) (Ar)3d5 3 d5 is more stable than 3d6 because the 3d6 subshell has two paired electrons which results in repulsion/pairing of electrons is (energetically) less favourable
Invertebrates use a copper complex, haemocyanin, to transport oxygen. Blue oxyhaemocyanin gives invertebrate blood its characteristic color. Explain why oxyhaemocyanin and oxyhaemoglobin have different colors.
The energy difference between the two sets of 3d orbitals is different Because the ligands/ions are different So radiation/light is absorbed from different regions of the visible spectrum
Explain why copper is classified as a d-block element
The final electron added is placed in a (3) d orbital
Explain how a change in energy levels causes complex ions to have different colors
The gap between groups of energy levels is different with different ligands/The 3d orbitals split to different extents with different ligands Electrons absorb/gain energy of specific frequencies when moving from lower to higher levels Color seen depends on the energy/frequency gap (between the two groups of energy levels)
Explain why phenylamine is a weaker base than ammonia
The lone pair on the nitrogen atom overlaps with delocalised electrons so the nitrogen atom is less able to accept a hydrogen ion
Evidence for structure of benzene
Thermochemical Data: Benzene does not have 3 discrete double bonds + considerably more stable than expected (Hydrogenation of cyclohexene = -120, expect hydro of cyclo - 1,3,5 - triene = 360 but hydro of benzene = -208) X ray diffraction: All bond lengths are the same Bond length is between a discrete C=C and C-C (C-C > 154, C=C > 134, Benzene > 139) Infra-Red Data Benzene + other arenes have several peaks but none for C=C (of cyclohexene at 1650)
Why is a support medium used?
To increase surface area (Ex: honeycomb mesh in catalytic converters)
Linear
Tollen´s reagent (Ag(NH3)2)+ 180 bond angle
Test for aldehyde
Tollen´s reagent Silver mirror
Reaction of bromine (liquid) with benzene
Two reactions: AlBr3 + Br2 Observations AlBr3 + Br2 > 2FeBr3 FeBr3 + Br2 > FeBr4- + Br+ (Electrophile) Benzene + Br+ > Benzene - Br + H+ (Bromo benzene) Fe + Br (Iron Filings) 2Fe + 3Br2 > 2FeBr3 FeBr2 + Br2 > FeBr4- + Br+ (Electrophile) (Same product) (H + + AlBr4- > AlBr3 + HBr H+ + FeBr4- > FeBr3 + HBr)
Suggest how iron (II) ions lower the activation.
Uncatalysed reaction involves two negatively charged ions reacting and catalysed steps involve oppositely charged ions reacting (which is kinetically more favourable/lowers the activation energy)
Oxidation states of Vanadium in VO2+, VO^2+, V3+, V2+ (with colors)
VO2+ = yellow +5 VO^2+ = green +4 V3+ = blue +3 V2+ = violet +2 Zn will reduce VO2+ > V2+ Sn will reduce VO2+ > V3+ but not V2+
Reaction of oxygen in air with benzene
Very smoky flame
Test for primary alcohol
Warm with acidified K2Cr2O7 > Orange to Green Distill product Test w/Tollen´s Reagent > Silver mirror
Test for secondary alcohol
Warm with acidified K2Cr2O7 > Orange to Green Test product with Tollen´s Reagent > No silver mirror
Conversion of acyl chloride to carboxylic acid
Water RT
Ligand exchange
When a stronger ligand is added or the concentration of a ligand is high enough to cause a ligand exchange to occur. Often leads to a preciptate redissolving or a change in color in the solution.
Amines miscibility with water
Will form hydrogen bonds so generally dissolves As chain length increases, becomes less soluble CH3NH2 + H2O > CH3NH3+ + OH- Weakly alkaline solution
Amines formation of salts
Will neutralize acids forming salts CH3CH2 + HNO3 > CH3NH3 (+ ON N) + NO3- Ionic solids
Why solutions on agua M3+ ions are acidic in water?
With M2+, only reacts with OH or NH3 ligands but with M3+ ion, the stronger the attraction between the M3+ and the water ligand, it weakens the OH bond significantly meaning H3O+ ions may be produced
Amphoteric Behaviour of Zinc (Zn)
Zn(H2O)4(OH)2(s) + 2OH-(aq) > (Zn(H2O)2(OH)4)2+ + 2H2O Zn(H2O)4(OH)2(s) + 2H+(aq) > (Zn(H2O)6)2+
Arenes contain a ___________ ring
benzene
Demonstrate an understanding of the functional group in an amide including several examples
carbonyl group on the C attatched to the NH Ethanamide
Transition metals are well known in the industry for being used as catalysts for their ability to ?
change oxidation state
Diamminecopper(I) ions are not coloured because
d-d transitions are not possible because the d orbitals are fully occupied
A ligand must be an electron pair ?
donor
The ? E cell value the more easily the species is oxidised
negative
The ? E cell value the more easily the species is reduced
positive
An imporant advantage of the use of polymer supports in organic synthesis by the pharmaceutical industry is that ?
the products are easily separated from the polymer support
