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AS Level Chemistry > deck_2925610 > Flashcards

deck_2925610 Flashcards

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1
Q

What are the the three types of alcohols?

A

Primary, secondary and tertiary.

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2
Q

How is it decided whether an alcohol is primary secondary or tertiary?

A

Primary means the OH group is bonded to a carbon which is bonded to one more carbon. Secondary means the carbon is bonded to 2 other carbons and tertiary it three other carbons.

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3
Q

How can a halogenalkane be made with an alcohol?

A

Replace the OH functional group with a halogen.

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4
Q

Which is the most reactive type of alcohol?

A

Tertiary ones. This means making halogenalkanes is easier with them.

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5
Q

Why are tertiary alcohols more reactive?

A

This is because when they react they lose the OH group and have a positive open bond. The tertiary alcohol will have electrons from other carbons pulled towards it meaning it is made weaker and so it lasts longer, meaning it can reacte.

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6
Q

What would be a simple way of making a choroalkane?

A

Shake a tertiary alcohol with HCl. This gives an impure chloroalkane as the OH that the Cl replaces will react with the H of the acid to form water.This principle happens with all hydrogen halides

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7
Q

What is the general equation of using phosphorous (III) halides to make halogenalkanes from alcohol?

A

3ROH +PX”3” = 3RX + H”3”PO”3”The X represents Cl, Br or I.R is just the rest of the alcohol or alkyl group.

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8
Q

What is the test for the hydroxyl group (-OH) ?

A

Add phosphorus (V) chloride.If -OH is present, steamy fumes of HCl gas will form. This gas should turn damp blue litmus paper red.

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9
Q

What is the equation to make chloroalkanes from alcohol with phosphorus(V) chloride?

A

ROH + PCL”5” = RCl + HCl + POCl”3”Everything is a liquid apart from the hydrochloric acid, which will be a gas.

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10
Q

What is formed when sodium reacts with alcohols?

A

Alkoxides are formed. The longer the hydrocarbon chain, the less reactive it is.

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11
Q

Give the equation of sodium reacting with ethanol.

A

2CH”3”CH”2”OH +2Na = 2CH”3”CH”2”O-Na+ and H”2”

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12
Q

What happens when sodium reacts with ethanol?

A

The OH bond is broken and ionic sodium ethoxide and hydrogen gas are produced.

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13
Q

Why do alcohols have high boiling points?

A

They have the OH functional group. This means the oxygen will pull electrons towards it resulting with slightly positive hydrogens. These will then bond with other oxygens meaning there are many strong hydrogen bonds, thus a high boiling point.

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14
Q

What can happen when an alcohol is mixed with water?

A

Hydrogen bonds may form between the OH and H”2”O.In small chain alcohols(methanol, ethanol, propan-1-ol) the hydrogen bonds means it can mix readily with water. It is miscible.

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15
Q

Why don’t longer chained alcohols mix with water?

A

Most of the molecule is a non polar carbon chain, thus there is less attraction with the H”2”O molecules.

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16
Q

What happens when alcohols are burnt in air?

A

They react with the oxygen to produce water and CO”2”

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17
Q

What can be used to oxidise an alcohol?

A

An oxidising agent like acidified potassium dichromate (VI) is oxidise is mildly.

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18
Q

What will primary alcohols oxidise to?

A

Aldehydes and then to carboxylic acid.

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19
Q

What will secondary alcohols oxidise to?

A

Ketones

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20
Q

What are aldehydes, ketones, and carbonyl compounds?

A

They have the functional group C=O and they all have the general formula C”n”H”2n”OAldehydes have a hydrogen and one alkyl group attached to the carbon carbonyl atom.Ketones have two alkyl groups attached to the carbon carbonyl atom.

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21
Q

What is a volatile substance?

A

Something that will react at low temperatures.

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22
Q

What is the only way to oxides tertiary alcohols?

A

Burn them.

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23
Q

How would you oxidise a primary alcohol to make a aldehyde?

A

Gently heat ethanol with potassium dichromate(VI) in a round bottom flask. Distill the product and collect the product.

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24
Q

How would you oxidise an alcohol to make a carboxylic acid?

A

Put the alcohol, oxidising agent and anti bumping granules in a round bottom flask.Fit a reflux condenser on top and heat.This means no volatile solvents reactants or products are lost.

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25
Q

What is a reflux condenser?

A

A condenser that is fitted vertically to a flask to stop any of the vapours from getting out.

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26
Q

How can a secondary alcohol be oxidised?

A

Add an oxidising agent and reflux. This will produce a ketone.

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27
Q

Can a ketone be oxidised by refluxing?

A

No.

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28
Q

How are aldehydes and ketones distinguished?

A

Using an oxidising agent like Benedict’s solution(also know as Fehling’s solution) and Tollen’s reagent.

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29
Q

How is Benedict’s solution used to tell the difference between aldehydes or ketones?

A

They are both deep blue Cu2+ complexes which are reduced to red Cu”2”O when warmed with an aldehyde but stay blue with a ketone.

30
Q

How is Tollen’s solution used to tell the difference between aldehydes or ketones?

A

It’s reduced to silver when warmed with an aldehyde but not with a ketone. The inside of the apparatus will be coated with silver.

31
Q

What is an alcohol called it has more than hydroxyl group?

A

It will be a diol or a triol.

32
Q

How would you dehydrate an alcohol?

A

Soak the alcohol in ceramic fibre and put in the bottom of a boiling tube. Hold horizontally and place aluminium oxide (Al”2”O”3”) granules in the middle. Put a tube on the end and put in a basin of water with a test tube on top to collect the gas.Gently heat the fibre.

33
Q

What is the equation of sodium reacting with methanol?

A

Na+ CH”3”OH = H”2” + CH”3”ONa

34
Q

What is the formula for sodium dichromate ?

A

Na”2”Cr”2”O”7” 2-

35
Q

When sodium dichromate oxidises an alcohol, what will it produce and what is the colour change?

A

The sodium dichromate will go from orange to green. Cr 3+ and water will defiantly be produced.

36
Q

What alcohols will sodium dichromate react with ?

A

Primary and secondary but not tertiary.

37
Q

What is the functional group of a aldehyde ?

A

CHO. (The carbon and the oxygen have a double bond between them)

38
Q

What will an aldehyde produce when reacted with water?

A

A carboxylic acid, electrons and hydrogen gas.

39
Q

Why are alcohols more reactive than alkanes?

A

The C-O and O-H bonds are easier to break than the C-H and C-C bonds.There also also polar.

40
Q

How could an alcohol be dehydrated chemically?

A

Gently heat with concentrated phosphoric or sulphuric acid.

41
Q

What is the functional group of carboxylic acid?

A

COOH. It is similar to that of an aldehyde. There is an oxygen double bonded to the carbon. There is also another oxygen with a single bond to the carbon and this also has a hydrogen bonded to it.

42
Q

What are primary,secondary and tertiary halogenalkanes?

A

A primary one will have the halogen attached to a carbon bonded to one another carbon.A secondary one will have 2 carbons attached and a tertiary one will have 3 carbons attached to the one the halogen is bonded to.

43
Q

What happens when a halogen alkane reacts with water?

A

It will form an alcohol.

44
Q

What is the general equation of water reacting with a halogenalkane?

A

R-X + H”2”O = R-OH + H+ and X-X= halogen.R= rest of halogenalkane

45
Q

How can the reactivity of a halogenalkanes be compared?

A

Put silver nitrate solution in the mixture of water and halogenalkane. The positive silver ions will react with the negative halogen to form a solid silver halide precipitate. The faster the precipitate forms, the more reactive it is.

46
Q

What can halogenalaknes be used for?

A

They can be used to make useful polymers.They are used as refrigerants.The non flammable are used as fire or flame retardants.

47
Q

Give examples of halogenalkanes being used to make polymers.

A

Chloroethene can be used to make poly(Chloroethene)Tetrafluoroethene can be used to make poly(tetrafluroethene) which is the coating used in non stick pans.

48
Q

Why are some halogenalkanes good refrigerants ?

A

They don’t corrode pipe work and are easily compressed.

49
Q

Why are carbon halogen bonds polar?

A

Halogens are more electrognegative than carbon, thus they are slightly negative while carbon is slightly positive.

50
Q

Why do halogenalkanes react readily with nucleophiles?

A

The carbon the halogen is bonded to is slightly positive and doesn’t have enough electrons. This means the nucleophile will be substituted for the halogen. The nucleophile provides a pair of electrons for the carbon while both the electrons in the halogen carbon bond go to the halogen which falls off as the nucleophile replaces it.

51
Q

What are some nucleophiles that react readily with halogenalkane?

A

OH- and NH”3”. Water can act as a weak nucleophile.

52
Q

Explain the reaction of halogenalkanes with aqueous alkalis.

A

The alkali provides an OH- that replaces the halogen to form an alcohol.The halogenalkane is refluxed with the alkali(like potassium hydroxide) and this provides a negative OH ion with 2 free electrons. This will react with the sigma positive carbon and will bond with it. A halogen with 2 free electrons and a -1 charge would be produced.

53
Q

Explain the reaction of halogenalkanes with aqueous alkalis. It substitutes

A

The alkali provides an OH- that replaces the halogen to form an alcohol.The halogenalkane is refluxed with the alkali(like potassium hydroxide) and this provides a negative OH ion with 2 free electrons. This will react with the sigma positive carbon and will bond with it. A halogen with 2 free electrons would be produced.

54
Q

Why do larger halogenoalkanes have higher boiling points?

A

The larger the molecule the more electrons there are in it. This means there are larger and more temporary dipoles that have to be overcome.

55
Q

How does the halogen in a halogenoalkane affect the boiling point?

A

The larger the halogen the greater the no. of electrons in the molecule.This means there are larger and more temporary dipoles that have to be overcome.

56
Q

Which is the only halogen that has the same electronegativity as carbon?

A

Iodine.

57
Q

How can the shape of a halogenoalkane affect the boiling point?

A

If it is long and thin, there is a larger surface area and the molecules can get closer together if it was round. Thus there are greater dispersion forces.

58
Q

Do halogenoalkanes dissolve in water? Why?

A

They don’t as the hydrogen bonds in the water will have to be broken and the van der waals and permanent dipoles in the alkane will have to be broken as well.

59
Q

Why might you think fluroalkanes are reactive?

A

There is a very positive carbon and negative fluorine. Then something fully negatively charged could displace the fluorine and bond with the positive carbon. However this doesn’t work.

60
Q

What dictates the reactivity of a halgenoalkane?

A

The size of the halogen. The smaller it is the closer it is to the carbon and so the stronger the bond.

61
Q

If I wanted to make a chorloalkane by adding HCl to an alcohol what would I have to be weary of?

A

It would only work with a tertiary alcohol. The other ones would take too long.You would also have to shake it.

62
Q

How would you make a bromoalkane from a primary alcohol?

A

Add sulfuric acid and cool by running under a tap. Add powered potassium bromide.Gently heat and distill. This works by creating HBr.

63
Q

When you have created a chloroalkane by using HCl, do you purify it?

A

Add anhydrous calcium chloride. Shake and put in separating funnel. Remove lower layer.Add sodium hydrogen carbonate in the funnel and shake. Remove the lower layer. Repeat the process until there is no fizzing.Add anhydrous sodium sulfate.

64
Q

What is the solvent used when reacting an aqueous alkali with a halgenoalkane?

A

A mixture of water and ethanol as halogenoalkanes won’t dissolve in water.

65
Q

If you want to favor elimination, what conditions do you have?

A

higher temperaturesa concentrated solution of sodium or potassium hydroxidepure ethanol as the solvent

66
Q

If you want to favor substitution , what conditions do you have?

A

lower temperaturesmore dilute solutions of sodium or potassium hydroxidemore water in the solvent mixture

67
Q

How would you react a halogenalkane with ammonia?

A

Heat in a sealed tube with the ammonia in a solution ofethanol. It isn’t heated in reflex as the ammonia would escape.

68
Q

Explain the reaction of a halogenalkane with ammonia.

A

It is a substitution reaction and will produce an amine and a hydrogen halide.This halide will react with excess ammonia to form ammonia salt.

69
Q

Explain the reaction of 1-bromobutane with ammonia.

A

The Br will be replaced with a nitrogen atom bonded to 2 other hydrogens. There will be HBr that will react with another NH₃ to form NH₄⁺Br⁻.

70
Q

What is a Bunsen valve?

A

Used when dehydrating something to prevent blowback. It is a piece of rubber tubing with a glass stopper. The rubber tubing has a slit cut in it so gas can get out but water can’t get in.

AS Level Chemistry (16 decks)

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