Paper 2 Misconceptions Flashcards by Noor Ghufran

Why is TMS used as a reference standard for chemical shifts?

Generates one sharp peak always found on far right of spectrum.
Highly volatile and unreactive

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What does number of peaks tell you on C13 NMR and H1 NMR?

Number of environments

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What does the location of the peaks tell you in C13 NMR and H1 NMR?

Type of proton environment

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What does the integration value/area under each peak tell you for H1 NMR?

Number of H+ in the environment

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What does the splitting tell you in H1 NMR?

Number of H+ in adjacent environments

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Singlet

No H next to it

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What solvent do we use when testing NMR of hydrogen based substances?

D2O
CCl4

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Problems with nucleophilic subs with excess NH3 to produce primary amine

Further substitution to produce a secondary tertiary or quaternary amine

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Problems with nucleophilic subs with KCN and reduction to produce primary amine

KCN is toxic, lower percentage yield and is 2 steps

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Uses of quaternary ammonium salts

Hair conditioner

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Longer the carboxylic acid chain is the..

less soluble it is- hydrocarbon chain is longer and insoluble

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Uses of esters

Plasticisers
Perfumes
Flavourings

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Ester formation reaction conditions and reagent

H2SO4 catalyst
Water byproduct
Warm and reflux

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Acid catalysed hydrolysis of ester

Carboxylic acid and alcohol

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Base catalysed hydrolysis of ester

Salt of carboxylic acid and alcohol

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Use of carboxylic acid salt formed from base hydrolysis of triester

Soap

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Use of biodiesel

Conserve crude oil supplies
Reduce amount of CO2 released

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Why are acid anhydrides used more commonly than acyl chlorides

Less corrosive
Side product is COOH not HCl

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Outline essential features of fractional distillation of crude oil that enables crude oil to be separated

Compounds have diff BPS
BP depends on length of compound
Hotter at bottom of column
Heavier molecules condense and collect at bottom

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Reaction mixture still reacting in continuous monitoring method. How do we solve this?

To stop reaction, QUENCH.
Add large volume of cold, distilled water to both cool and dilute the reaction, reducing the rate.

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The volume of gas produced from a reaction could be measured at regular intervals. What is the problem with this?

Records amount of product produced when this order of reaction is about reactants, so the volume would need recording into reactant conc.

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Continuous monitoring graph labels and how to measure progress of reaction

Conc v time
- Take samples at regular intervals
- Use visible indicator such as gas volume

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Initial rates graph labels and key points

Rate v conc
Volume ∝ Conc
When total volume is constant, the volume of reactant is proportional to its conc

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Properties of ordinary PVC vs plasticiser PVC

PVC is made of long, closely packed together polymer chains- hard and brittle. Used in drain pipes.

Plasticiser PVC is more flexible- used for electrical cable insulation and clothing

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Mechanical recycling

Plastics sorted into different types and washed Ground into pellets Pellets melted down and remoulded into new objects

Feedstock recycling

Plastics sorted into different types Heated to temp which breaks their polymer bonds Repolymerised to form new plastics

Addition polymer

An Addition Polymer is a long chain formed from many monomers and no other product is formed.

Condensation polymer

In a condensation reaction, two molecules join to form a larger one, with a small molecule such as H2O or HCl being released

Two types of condensation polymer

Polyamide Polyester

Uses of terylene

Carpets Clothing

Uses of nylon and properties

Used as fibres in clothing Elastic, strong abrasion resistant

Uses of kevlar and properties

Used in manufacture of body armour and crash helmets Strong, light, heat resistant

Why are addition polymers not biodegradable?

Have non polar C-C bonds that cannot be hydrolysed

Why are condensation polymers biodegradable?

They can be hydrolysed under acidic or basic conditions Delta positive C of polar C-O bond can be attacked by nucleophiles

Acid hydrolysis of polyamide

NH3+ and COOH

Base hydrolysis of polyamide

COONa and NH2

Acid hydrolysis of polyester

OH and COOH

Base hydrolysis of polyester

COONa and OH

Acidic conditions for amino acids

Protonated so become NH3+ including R group

Alkaline conditions for amino acids

Deprotonated so COO- including R group

What are enzymes described as?

Stereospecific

How can the amount of further substitution be reduced?

Excess of alkane used

Properties of CFCs

non-toxic inert gases volatile

Primary alcohol to Aldehyde

1 [O] Distillation

Primary alcohol to carboxylic acid

2 [O] Reflux

Aldehyde to carboxylic acid

1 [O] Reflux

Secondary alcohol to ketone

1 [O] Reflux

Advantage of hydration of ethene

Large scale continuous production method

Disadvantage of hydration of ethene

High temp and pressure needed- increases cost

Advantage of fermentation

Uses renewable resources

Disadvantage of fermentation

Slow rate of reaction

Advantage of biofuels

Come from raw renewable materials to conserve crude oil supplies

Disadvantage of biofuels

Many other carbon costs in their production so they aren't carbon neutral (CO2 released during transportation and distillation)

Use of condenser

Water passes around outside tube w distillate to cool it

Use of antibumping granules

Prevents large bubbles from forming

Why is reflux used to oxidise alcohol into carboxylic acid

Reflux doesnt allow any reactant vapour to escape

OH in alcohols

Finger like/Test tube shape

OH in acids

Mitten shape

Where is the fingerprint region?

Fingerprint region is the area of the spectrum below 1500cm-1

Dynamic equillibrium

Forward and backward reaction occur at equal rate Conc of reactants and products is constant

EMP

Most likely energy of particles in a sample

Emean

Mean energy of particles

Why does kinetic energy graph start from origin?

No particles have no energy

Higher temp graph KE

Curve shifts right Peak lower Area under curve beyond activation energy increases

Lower conc graph KE

Peak lower Area under curve smaller

Formation of primary amine in 2 steps

Nucleo subs Haloalkane to nitrile Reduction using H2 and Ni catalyst

Formation of phenylamine

Electrophilic substitution to form nitrobenzene Reduction using Sn and conc HCl

Is secondary or primary carbocation more stable?

Secondary

Explain why a nucleophile would attack a haloalkane with Br in a nucleophilic substitution reaction

Bromine more electronegative than carbon C is electron deficient Lone pair on nucleophile donated to electron-deficient carbon

Explain the bonding in and the shape of a benzene molecule

Stage 1 Bonding 1a) Each C has three (covalent) bonds 1b) Spare electrons (in a p orbital) overlap (to form a pi cloud) 1c) delocalisation Stage 2 Shape 2a) Planar 2b) Hexagon/6 carbon ring/120o bond angle 2c) C–C bonds equal in length / C–C bond lengths between single and double bond Stage 3 Stability 3a) Expected Ho hydrogn of cyclohexatriene = –360 kJ mol–1 3b) Ho hydrogn benzene (is less exothermic) by 152 kJ mol–1 3c) Benzene lower in energy than cyclohexatriene / Benzene is more stable

Two ways of maximimising yield of propanal by distillation of reaction mixture

Cool distillate Keep temp of reaction mixture below bp of the thing added e.g. propan-1-ol