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39 Cards in this Set
- Front
- Back
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Why do we accept the delocalised model of benzene?
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X-ray studies --> Bond length
ΔHhydrogenation = -208, not -360 (benzen more stable than expected) No reaction with Br₂ - Insufficient electron density to polarise Br-Br bond. |
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Draw out the electrophilic substitution mechanism of arenes with conc HNO3 and H₂SO₄ and a halogen in the presence of a halogen carrier
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p4/5 in revision book
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What is the equation for the formation of the NO₂⁺ electrophile?
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H₂SO₄ + HNO₃ --> HSO₄⁻ + NO₂⁺ + H₂O
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What is the equation for the formation of the X⁺ electrophile? (Where X is a halogen)
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X₂ + AlCl₃ --> X⁺ + AlCl₄⁻
(Heterolytic fission of X₂) |
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What is a suitable halogen carrier?
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AlCl₃
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Why is benzene resistant to bromination compared with alkenes?
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The delocalised electron density Benezene's pi bonds are insufficient to polarise X₂
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Phenol + Alkali(aq)/Na -->
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Salt
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Phenol + 3Br₂ -->
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2,4,6-tribromophenol) + 3HBr
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Why is it easier to brominate phenol compared with benzene?
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An electron pair is donated to the benzene ring from an oxygen p-orbital :)
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What are phenols used for?
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Plastics, antiseptics, disinfectants, resins for paints
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What is used to oxidise alcohols?
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K₂Cr₂O₇/H⁺
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Primary alcohol + [O] --> (distil and reflux)
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Distillation: Aldehyde (-CHO)
Reflux: Carboxylic Acid (-COOH) |
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Secondary alcohol + [O] -->
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Reflux: Ketone
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What is the compound used to reduce carbonyl compounds? What's formed?
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NaBH₄, primary/secondary alcohol
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Draw out the nucleophilic addition mechanism in reactions of aldehydes and ketones with hydrides
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p8 in revision guide
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What is 2,4-DNPH used for? (BRADY'S reagent)
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Detect the presence of a carbonyl group in an organic compound
Identify a carbonyl compound from the melting point of the derivative |
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What is Tollens' reagent? (Compound and usage)
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Ammonical silver nitrate
Detect presence of an aldehyde group Distinguish between aldehydes and ketones. Aldehydes are oxidised to carboxylic acids with deduction of silver ions to silver (learn) |
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Why are carboxylic acids soluble in water?
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Due to hydrogen bonding and dipole-dipole interaction.
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Carboxylic Acid + Metal -->
CH₃COOH + Na --> |
Salt + Hydrogen
CH₃COO⁻Na⁺ + ½H₂ |
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What is the bond angle and shape of the -COOH group?
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Trigonal planar, 120⁰
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Acid anhydride + alcohol <-->
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Ester + Carboxylic Acid
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Carboxylic acid + alcohol <-->
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Ester + Water
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Carboxylic acid + Carbonate -->
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Salt + Water + Carbon Dioxide
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Carboxylic acid + Base -->
CH₃COOH + NaOH --> |
Salt + Water
CH₃COO⁻Na⁺ + H₂O |
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Ester + Hot Alkali(aq) --hydrolysis-->
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Carboxylic acid + Alcohol
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Acid + Alcohol <--> Ester + Water requires a....
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H⁺ catalyst
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Ester + Hot Acid(aq) --hydrolysis-->
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Carboxylate + Alcohol
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What are esters used for?
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Perfumes and flavourings
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What is a triglyceride?
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A triester of glycerol (propane-1,2,3-triol) and fatty acids
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How do you form a trans fat? What's the issue with trans fats?
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When hydrogen is added to vegetable oil (hydrogenation) - this type of fat is associated with raising the levels of low-density lipoprotein
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What are esters of fatty acids used for? What's the technical name?
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Biodiesel - Re-read the question. This process is known as TRANSESTERIFICATION! (Gold!) - Transesterification is the reaction between triglycerides and another alcohol to form esters of the alcohol and glycerol.
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Why are amines basic?
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Protons are accepted by the nitrogen lone pair
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Amine + Acid -->
CH₃CH₂NH₃ + HCl --> |
Salt
CH₃NH₄⁺Cl⁻ (ethylammonium chloride) |
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Amines are a special type of base, what's the name?
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Bronsted-Lowry base (a species with the ability to gain or 'accept' a hydrogen cation (proton))
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How do you prepare aliphatic amines?
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Substitution of halogenoalkanes with excess ethanolic ammonia
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How do you prepare aromatic amines?
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Reduction of nitroarenes using tin and concentrated hydrochloric acid
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How do you synthesise an azo dye?
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By reaction of an aromatic amine with nitrous acid (HNO₂) (<10⁰C) with formation of a diazonium reaction. The react in a coupling with phenol in alkaline conditions (NaOH)
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What is generated in situ in the synthesis of azo dyes?
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Nitrous acid (HNO₂) - From NaNO₂ /HCl
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What are azo dyes used for?
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Dyestuffs
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