Alcohols, Haloalkanes & Analysis

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  • Created by: meganlyy
  • Created on: 06-01-18 23:00
Why are alcohols polar molecules?
The O is more electronegative so pulls electrons towards itself making the C and H delta positive.
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Why are smaller chain alcohols soluble in water?
H-bonds form between water and -OH group. Lone pairs on the O in both -OH and water form H-bonds with the Hs from both molecules. In larger alcohols, most of the chain is the R group which doesn't form H-bonds with water, so less soluble.
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Why do alcohols have low volatility?
Alcohols can form H-bonds with themselves so have high boiling points and doesn't evaporate easily.
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How is a haloalkane formed from an alcohol?
Reacts with compounds containing halide ion where -OH is substituted by halide ion, and requires acid catalyst.
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What happens when alcohols are dehydrated?
Alkenes are formed when water is eliminated from alcohols, and conditions are heat and either conc sulfuric acid or conc phosphoric acid. Water molecule made from -OH and H which was bonded to C next to -OH group.
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What's the easiest way to oxidise alcohols and what is formed?
Easiest way is to burn them in combustion reaction which forms water and carbon dioxide.
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What oxidising agent is used to oxidise alcohols mildly?
Acidified potassium dichromate.
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What are primary alcohols oxidised to?
Can be oxidised twice. Distil to form aldehyde and reflux to form carboxylic acid.
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What are secondary alcohols oxidised to?
Reflux to form ketone.
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What are tertiary alcohols oxidised to?
Nothing.
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What colour does alcohol solution turn when oxidised with acidified dichromate?
From orange to green.
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Are haloalkanes polar molecules?
Haloalkanes are polar because halogen is more elctronegative making the C delta positive.
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What kind of reaction do haloalkanes undergo?
Nucleophilic substitution because of the delta positive C.
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What are nucleophiles?
Electron pair donor, can be neagtive ion or atom with lone pair of electrons, OH-, CN-, NH3 and water but reacts slowly.
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Haloalkanes can be hydrolised, what are the conditions and reagent for this reaction?
Reacts with warm aqueous alkali, as the OH- ion substitutes the halogen, and under reflux.
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What is formed when a haloalkane reacts with water?
Alcohol is formed as OH- substitutes halogen.
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Which type of haloalkanes hydrolise the fastest and why?
Iodoalkanes hydrolise the fastest because the halogen-carbon bond is the weakest as the bond enthalpy is the lowest.
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How to test for the most reactive haloalkane?
Mixing haloalkane with water forms alcohol and X-, by adding silver nitrate solution silver ion and halide ion form precipitate. Yellow precipitate of iodine forms first.
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What are CFCs?
Chloroflourocarbons, have no hydrogens and destroy ozone layer.
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What is ozone and how is it formed?
Ozone is O3, acts as chemical sunscreen as it absorbs UV radiation. Formed when O2 breaks down into free radicals by UV, and then O free radical attacks O2 molecule to form O3.
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How are chlorine free radicals formed and how does it destroy ozone layer?
When C-Cl bond is broken by UV Cl free radical formed. Reacts with O3 giving O2 and ClO radical. ClO radical then reacts with O forming O2 and Cl free radical.
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What is the overall reaction of chlorine radical and O3?
O3 plus O forms 2O2. Cl radical acts as catalyst.
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How do nitrogen oxides break ozone down?
Nitrogen oxides form NO free radical which acts as a catalyst.
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Other cards in this set

Card 2

Front

Why are smaller chain alcohols soluble in water?

Back

H-bonds form between water and -OH group. Lone pairs on the O in both -OH and water form H-bonds with the Hs from both molecules. In larger alcohols, most of the chain is the R group which doesn't form H-bonds with water, so less soluble.

Card 3

Front

Why do alcohols have low volatility?

Back

Preview of the front of card 3

Card 4

Front

How is a haloalkane formed from an alcohol?

Back

Preview of the front of card 4

Card 5

Front

What happens when alcohols are dehydrated?

Back

Preview of the front of card 5
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