Chemistry- Alcohols and Alkenes (3.2)

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Primary Alcohols
OH is attached to carbon with 1 R group (alkyl group/ other carbon) attached to it.
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Secondary Alcohols
OH is attached to carbon with 2 R groups (alkyl group/ other carbon) attached to it.
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Tertiary Alcohols
OH is attached to carbon with 3 R groups (alkyl group/ other carbon) attached to it.
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Oxidising Alcohols
Potassium or sodium dichromate dissolved in sulfuric acid will act as an oxidising agent. If oxidation occurs, orange solution containing dichromate ions is reduced to green solution containing chromium ions.
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Oxidising Primary Alcohols
First oxidised to an aldehyde and then further oxidised to a carboxylic acid. Can control how far alcohol is oxidised by controlling reaction conditions (distillation or reflux).
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Oxidising Secondary Alcohols
Oxidised to ketones. Cant be oxidised futher as C-C bond would need to be broken, so prolonged reflux wont produce anything more.
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Oxidising Tertiary Alcohols
Cant be oxidised due to strong C-C bond and no H atoms available to be lost. Solution stays orange. Only way to oxidise tertiary alcohols is to burn them.
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How and why can you distinguish between aldehydes and ketones?
Use oxidising agents as aldehydes are easily oxidised to carboxylic acids, whereas ketones aren't. Ketones can't be easily oxidised because they don't have a H bonded to the C. Presence of carboxylic acid can be tested w/ Na2CO3, produces CO2.
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Fehling's Solution
Blue Cu2+ complex (copper (II) ions dissolved in sodium hydroxide). Reduces to brick-red Cu2O precipitate w/ an aldehyde, stays blue w/ ketone.
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Benedict's Solution
Blue Cu2+ complex (copper (II) ions dissolved in sodium carbonate). Reduces to brick-red Cu2O precipitate w/ an aldehyde, stays blue w/ a ketone.
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Tollen's Reagent
Colourless solution of silver nitrate and ammonia Ag(NH3)2. [Ag(NH3)2]+ complex reduced to silver when warmed w/ aldehyde (silver precipitate coats apparatus and forms mirror), but remains colourless w/ ketone.
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Acidified Potassium Dichromate
Aldehydes will be oxidised, and will reduce the Cr2O7 2+ (dichromate) ion to Cr3+ (chromium) ion. Orange--> green. Ketones will incure no colour change (stays orange).
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Dehydrating Alcohols
Alkenes made from alcohols by eliminating H2O. Ethanol heated w/ conc sulfuric/phosphuric acid under relfux. Lone pair from O bonds to H+ from acid. Alcohol accepts proton= O=+. + O pulls electrons from C. Carbocation loses H. C=C forms.
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Purifying Product from Dehydration of Alcohol
1. Reaction and 1st distillation- H2SO4+H3PO4+cyclohexanol+carbonumdum boiling chips. Distillation, heat to 83C. 2. Separation- Separating funnel, add water, drain off aqueous layer. 3. Purification- add anhydrous CaCl2 and distil to 83C.
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Ethanol Production- Hydration
Steam, solid phosphoric acid catalyst, 300C, 60atm. Pair of electrons from double bond bonds to H+ from acid. Lone pair from H2O bonds to carbocation. Water loses H+. Ethanol formed.
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Evaluation of Hydration to Produce Ethanol
+ Fast, pure, continuous process. - Crude oil= non-renewable resource. Requires lots of energy. Expensive equipment.
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Ethanol Production- Fermentation of Glucose
Yeast produces enzymes which converts glucose into ethanol and CO2. Anaerobic respiration- absence of air prevents extra reactions- oxidising ethanol to ethanoic acid. 30-40C.
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Evaluation of Fermentation of Glucose to Produce Ethanol
+ Sugar cane= renewable resource. Cheap equipment. Less energy required. - Slow. Impure. Batch process. High labour costs. Uses land that could be used to grow food crops.
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Biofuels
Fuel made from renewable, biological materials that have recently died. + Renewable resources. Carbon neutral (?). - Ethical (food vs fuel). Environmental (deforestation destroys habitats). Practical (car engines need to be modified).
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Is Bioethanol carbon neutral?
P/s, fermentation and ethanol burning processes are carbon neutral, because they use up and release exactly 6 moles of CO2- no net emission of carbon to atmosphere. But, fossil fuels burnt- fertilisers produced, glucose harvested, refined, transport.
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Alkenes
CnH2n. Unsaturated. 2 pairs of electrons in C=C, high electron density, reactive. C=C nucleophile (attracted to electrophiles w/o enough electrons.)
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Electrophiles
Attracted to negative charge, electron pair acceptor.
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Electrophilic Addition
Double bond opens up and atoms are added to C atoms. 1. 2 electrons from C-C attack H creating new bond C-H. H-Br breaks, electron taken by Br. Carbocation intermediate. 2. Br- acts as nucleophile, attacks carbocation, forming new bond.
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Electrophilic Addition- Hydrogenation
H added across C=C. 150C , nickel catalyst. Gaseous reactants. Veg/animal fats contain high proportions of unsaturated fats. C=C means don't fit well together. Hydrogenation increases boiling point= solid at room temp. High temps produces trans fats.
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Electrophilic Addition- Halogenation
Halogen molecule added across C=C. Room temp, alkene becomes saturated->dihaloalkane. Testing for unsaturation- orange bromine water-> colourless. Electrons from C=C attack Br, Br-Br breaks. C-Br forms, Br takes electron pair. Nucleophilic Br-.
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How do you know which products are going to be the most abundant when halogen halides are added to unsymmetrical alkenes?
Can form primary or secondary haloalkene. Amount of product formed depends on how stable carbocation formed in middle reaction is. Carbocations with more alkyl groups feed electrons towards positive charge. Stable secondary is more abundant.
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Heating Ethene with Water and Sulphuric Acid
1. Electrophilic addition- C=C attacks H, bond forms (H-C) electrons from O-H taken by O to form lone pair. C left with + charge (lost electron). Negative ion=nucleophile,attacks carbocation. 2. Hydrolysis- water, heat, forms ethanol+sulphuric acid.
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Addition Polymers
Double bonds open up and join together to make long chains. Unreactive (saturated and non-polar C chains). Longer chains w/ fewer branches have stronger IMF between branches= stronger/ rigid.
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PVC
Poly(chloroethene)/ polyvinyl chloride. Covalent bonds between Cl and C atoms are polar. Slight charges means permanent dipole-dipole forces= hard, but brittle= drain pipes/ window frames.
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Plasticisers
Chemicals which make polymers bendier, molecules get between polymer chains and push them apart, which reduces strength of IMF between chains= chains can slide around more= flexible= floor tiles/clothing.
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Disposal of Polymers
Burnt to generate electricity. Organic feedstock- broken down into useful smaller molecules. Biodegradable polymers- contain plant starch (microorganisms digest) and addition polymers. Bioplastics. Photodegradable polymers.
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Card 2

Front

Secondary Alcohols

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OH is attached to carbon with 2 R groups (alkyl group/ other carbon) attached to it.

Card 3

Front

Tertiary Alcohols

Back

Preview of the front of card 3

Card 4

Front

Oxidising Alcohols

Back

Preview of the front of card 4

Card 5

Front

Oxidising Primary Alcohols

Back

Preview of the front of card 5
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