Organic Chemistry 1 - Alkanes to Alcohols Flashcards

Question

What is the molecular formula of a dimethylethyl side chain?

Answer 1

-CH(CH3)CH2CH3

Answer 2

-CH2CH(CH3)2

Answer 3

1) Find the longest chain 2) Identify side chains 3) List side chains alphabetically 4) If more than 1 side chain of the same type is present, prefix it with di, tri etc. Ignore these when deciding alphabetical order 5) Number the side chains according to where they occur on the longest chain. Number the chain in the way that gives the lower number for the first side chain

Answer 4

Clear pattern - as the number of carbon atoms increases, the number of electrons increases so the strength of London forces increases, giving a higher boiling point

Answer 5

1 curve for even numbers of carbon atoms and 1 curve for odd numbers of carbon atoms. Even numbered chains pack together more efficiently than odd numbered chains , so melting points are higher for even numbered carbon chains

Answer 6

There are fewer points of contact in branched chain alkanes between adjacent molecules

Answer 7

No, immiscible liquids

Answer 8

Yes, similar structures

Answer 9

Crude oil is a mixture of hydrocarbons, mainly alkanes, and so they have different boiling points, so they can be separated using fractional distillation

Answer 10

Distillation flask, fractionating column, Liebig condense, receiver (conical flask which is changed to catch each distillate separately)

Answer 11

Collection is from various points on the fractionating column, the process is continuous rather than batch, and instead of using glass rods in the fractionating column, bubble caps are used

Answer 12

``` Refinery gases Gasoline (Petrol) Naphtha Kerosene Diesel oil Fuel oil Residue ```

Answer 13

Bottled camping gas

Answer 14

Fuel for cars

Answer 15

Making chemicals

Answer 16

Aircraft fuel

Answer 17

Fuel for cars, lorries and buses

Answer 18

Fuel for ships and power stations

Answer 19

Bitumen for roads and rooves

Answer 20

Halogenation, cracking, combustion

Answer 21

In presence of sunlight, a violent reaction takes placeto produce hydrogen chloride gas and various liquid halogenoalkanes are formed

Answer 22

Hydrogen chloride gas (always) - Chloromethane, CH3Cl (if methane is in excess) - Dichloromethane, CH2Cl2 - Trichloromethane, CHCl3 - Tetrachloromethane, CCl4 (if chlorine is in excess) Products can be separated using fractional distillation

Answer 23

A free radical is a neutral species which possesses an unpaired electron

Answer 24

Example of homolysis/homolytic fission where a covalent bond is split so that one electron of the pair goes to one group produced after splitting and one elctron goes to the other

Answer 25

To differentiate between the straight arrow used for a dative covalent bond

Answer 26

Cl-Cl splits under UV light to form 2Cl' | Only step of the reaction which requires sunlight so it is called a photolytic reaction

Answer 27

Propagation - in each step, a free radical reacts with a neutral molecule to give another free radical and a neutral molecule Termination - ends the reaction by reacting 2 free radicals to form a neutral molecule

Answer 28

The concentrations of chlorine radicals and methyl radicals are low in comparison with the concentration of neutral molecules, so the chances of a termination step are much lower than the chances of a propagation step. Many thousands of chlorinated molecules are formed for each chlorine molecule decomposed

Answer 29

Bromine reacts with methane in a similar way to chlorine. Fluorine reacts vigorously, often breaking down the carbon skeleton to give carbon and hydrogen fluoride. Iodine does not react

Answer 30

Carbon dioxide and water

Answer 31

Carbon monoxide and water, or sometimes just carbon (soot)

Answer 32

When an alkane is heated to a high temperature in the absence of air it breaks down to give and alkene and hydrogen, or an alkene and another alkane.

Answer 33

A high temperature (500-600°C) and has a free radical chain mechanism with initiation, propagation and termination steps

Answer 34

A slightly lower temperature (400-500°C) and a catalyst of usually silica/silicon oxide or alumina/aluminium oxide and has an ionic mechanism

Answer 35

- Saves energy by enabling the reaction to be carried out at a lower temperature - It allows the way in which the alkane breaks down to be much more controlled and by changing the catalyst you can change the products, as changing the temperature controls the reaction to a degree, but using catalysts does it much more

Answer 36

Alkanes can be used as fuels, but alkenes have much more uses such as making solvents and plastics

Answer 37

The processing of straight chain hydrocarbons into branched chain alkanes and cyclic hydrocarbons for efficient combustion

Answer 38

Passing the alkana over a catalyst. Changing the catalyst can change the product formed. A common catalyst is platinum supported on a base of aluminium oxide

Answer 39

Branched chain hydrocarbons burn more smoothly than straight chain hydrocarbons in petrol engines, so they are in higher demand

Answer 40

- Be abundant or easily manufactured - Ignite easily - Have high energy output - Be easily stored and transferred - Be non-toxic - Cause minimal environmental damage

Answer 41

- Volatile - Flow easily - Ignite easily

Answer 42

- Not very volatile - Do not flow easily - Do not ignite easily

Answer 43

A mixture of hydrocarbons laid down over millions of years through the anaerobic decay of animal and vegetable matter - coal, natural gas, crude oil

Answer 44

- Cannot be liquefied until -83°C - Found as a natural gas - Burns cleanly with few pollutants and least CO2 per unit than any other fuel except hydrogen - Can be piped directly into urban areas - Not suitable for vehicle fuel as it would have to be stored in large, high pressure cylinders

Answer 45

- Manufactured from natural gas by passing it over a heated catalyst, or from electrolysis of water (which requires energy) - The ways hydrogen is produced means it is a fuel derived from fossil fuels, as means of generating energy to produce it with wind or wave power are too expensive - Cannot be stored easily, so cannot be used in vehicles, and is too explosive to be used as a domestic fuel - Where energy per unit mass is critical liquid hydrogen (+liquid oxygen) are very good (e.g. in rockets)

Answer 46

- Found in natural gas and is produced when oil is cracked - As a liquid under pressure it is used as a fuel in motor vehicles (LPG - liquid petroleum gas), but cars have to be specially adapted to use it and specialist equipment has to be used - Butane produces less CO2 than petrol and leaves fewer unburnt hydrocarbons so is less polluting

Answer 47

- Obtained from crude oil - Most convenient fuel; easy to transport and store and are not dangerously volatile - High yield of energy per unit volume but produce much more CO2 than fuel like methane - CO is produced but can be removed by a catalytic converter, but the high pressure in the converter reduces the efficiency of changing chemical energy of the fuel into KE for the vehicle

Answer 48

A biofuel is a fuel made from renewable organic materials such as sugar, grain or vegetable oils

Answer 49

- Made by the fermentation of carbohydrates > First starch is broken down (from sugar cane, wheat etc) into glucose by heating with an acid catalyst or enzymes > Sucrose is converted into a mixture of glucose and fructose by enzymes in yeast > Other enzymes ferment glucose and fructose to produce a dilute solution of ethanol - The atom economy of the process is a maximum of 67% and the ethanol has to be obtained from the mixture by fractional distillation - energy demanding - Energy output is lower than that of petrol

Answer 50

- A vegetable oil is converted into biodiesel by mixing it with methanol and an acid catalyst, causing a transesterification reaction to take place. The methyl esters have similar combustion properties to diesel from crude oil and can be used purely, or mixed with diesel - Many crops can be used as a source of vegetable oil, but the fuel used to produce the crops as well as energy used to process the vegetable oil means biodiesel has a carbon footprint - Waste vegetable oil can be used as a source

Answer 51

The main problem with growing biofuels is that they use land which could be used to grow food, or they require destruction of natural forests. This can then push up the prices of food crops, affecting the poorest people in society

Answer 52

- They may not burn fuel completely - The fuel may contain impurities - They run at high enough temperatures that nitrogen and oxygen in the air can react

Answer 53

It is a toxic gas which combines strongly with haemoglobin, meaning the blood cannot absorb oxygen and so CO can be fatal in high doses

Answer 54

The soot formed includes fine particles and nanoparticles which are able to penetrate deep into the lungs, which causes short term symptoms (like headaches and coughing) and long term problems (liek heart disease and lung cancer), however, modern diesel engines use a diesel particulate filter to capture the carbon particles which are then burned

Answer 55

Unburned hydrocarbons may include benzene which is carcinogenic. In engines, careful monitoring of the air to fuel ratio entering the engine is used to minimise the release of unused fuel

Answer 56

Sulfur compounds are the main impurities in crude oil which should be removed before fuels are used in order to reduce sulfur dioxide emissions. Sulfur dioxide can cause acid rain and sulfur can damage the catalyst in catalytic converters

Answer 57

S + O2 -> SO2 then SO2 + H2O -> H2SO3 or// SO2 + 1/2O2 -> SO3 then SO3 + H2O -> H2SO4

Answer 58

When patrol vapour is burned, the temperature can rise to 2800°C, giving sufficient activation energy for nitrogen to react with oxygen to form nitrogen oxide (N2 + O2 -> 1/2NO). The NO then reacts to form nitrogen dioxide (NO + 1/2O2 -> NO2) The nitrogen dioxide can react with water and more oxygen to form nitric acid, leading to the production of acid rain (disproportionation)

Answer 59

In bright sunlight, NO2 molecules break down into NO and oxygen radicals, which combine with oxygen molecules to form ozone. Ozone is a pollutant on its own, but it can also mix with unburned hydrocarbons to form a mix of irritant chemicals which can build up to create a photochemical smog

Answer 60

They improve air quality by removing pollutants. In the presence of the catalyst, CO and unburned hydrocarbons react with nitrogen oxides to form CO2, H2O and N2. The converter has a honeycomb of ceramic material with a thin layer of metals (rhodium, platinum and palladium), and the large surface area increases the rate of reaction so that 90% of pollutant gases are removed

Answer 61

It is a compound which contains a multiple covalent bond e.g. a carbon carbon double bond or triple bond

Answer 62

One sigma bond and one pi bond

Answer 63

When alkenes react, the pi bond is broken, which is much weaker than the sigma bond

Answer 64

Compounds with the same molecular formula but different structural formulae - Chain isomerism - Position isomerism - Functional group isomerism

Answer 65

Compounds with the same molecular and structural formula but different arrangements of atoms

Answer 66

There must be 2 different groups attached to each double bonded carbon atom. These isomers occur because of restricted rotation round the carbon-carbon double bond

Answer 67

Groups around a carbon carbon or other rigid bond are ranked according to their atomic number. The atom with the higher atomic number has the higher priority. If the 2 high priority groups are on the same side of the double bond it is the Z isomer, and if they are on different sides it is the E isomer

Answer 68

If the 2 alkyl groups are on the same side of the bond then it is the cis isomer and if they are on different sides it is the trans isomer

Answer 69

- Slightly lower melting and boiling points than their corresponding alkanes - Alkenes with <5 carbon atoms are gases at room temperature, 5-15 are liquids and 15+ are solids - Alkenes are soluble in non-polar organic solvents, but are almost completely insoluble in water

Answer 70

A reaction that occurs when 2 substances react together to form a single substance

Answer 71

Electrophiles are species which are electron deficient (delta +) or have a positive charge and so can accept a pair of electrons from an electron rich site forming a new covalent bond

Answer 72

Reagent: hydrogen Conditions: nickel catalyst, 180°C, 2atm Product: alkane Reaction type: free radical addition

Answer 73

A palladium or platinum catalyst allows the reaction to take place at room temperature and pressure (rather than at 180°C and 2atm with nickel) but are much more expensive, and so are not viable on an industrial scale

Answer 74

It weakens the bonds between the hydrogen atoms which then add on across the double bond

Answer 75

It is used in the manufacture of margarine. Natural vegetable oils are unsaturated, and when reacted with hydrogen some of the C=C bonds become hydrogenated and become C-C, causing the vegetable oil to become a solid

Answer 76

``` Reagent: bromine Conditions: inert solvent (like hexane), room temperature Product: dibromoalkane Reaction type: electrophilic addition Bromine can be substituted for chlorine ```

Answer 77

Fluorine reacts very violently to produce CF4 and iodine reacts slowly and incompletely

Answer 78

In order to prevent free radical substitution

Answer 79

Using a solvent like hexane provides a common solvent for both reagents to dissolve in

Answer 80

There is attraction between oppositely charged ions

Answer 81

There would be no obvious colour change even though a reaction occurs

Answer 82

Reagent: hydrogen halide Conditions: mix gases at room temperature Product: halogenoalkane Reaction type: electrophilic addition

Answer 83

It follows the order of acid strength | HI > HBr > HCl > HF

Answer 84

In the presence of water, the halogenoalkane may be hydrolysed to form an alcohol

Answer 85

Rate increases HCl < HBr < HI. following order of increased acid strength. The first step of the mechanism determines the rate

Answer 86

Carbon cations with 1 alkyl group and 2 hydrogens attached. The least stable carbocations

Answer 87

Carbon cations with 2 alkyl groups and 1 hydrogen attached

Answer 88

Carbon cations with 3 alkyl groups attached. The most stable carbocations

Answer 89

The inductive (electron pushing) effect is explained by the difference in electronegativities of C (2.5) and H (2.1). The carbon of CH3 pushes electrons to the positively charged carbon ion, stabilising the charge on the carbocation

Answer 90

Alkyl groups tend to release electrons (electron releasing inductive effect) which stabilise carbocations. The more alkyl groups around a positive carbon ion the more it is stabilised, making tertiary carbocations (the one with the most alkyl groups attached) the most stable

Answer 91

(CH3)3C > (C2H5)(CH3)CH > C4H9 > C3H7 > C2H5 > CH3 > H More carbon atoms in a group = more the group releases electrons, branched chain alkyl groups = better at releasing electrons

Answer 92

The mechanism proceeds via the more stable carbocation

Answer 93

Reagent: Br2 (aq) Conditions: room temperature Product: bromoalcohol Reaction type: electrophilic addition

Answer 94

Rapid decolorisation of bromine water (orange to colourless). The main product is formed by the addition of OH and Br

Answer 95

Reagent: KMnO4 / dilute H2SO4 Conditions: acidified solution (dilute H2SO4), room temperature Product: diol Reaction type: oxidation

Answer 96

The alkene is oxidised and the products depend on the conditions. A dilute, acidified solution of potassium manganate (VII) converts an alkene to a diol at room temperature. The purple manganate ions are reduced to pale pink Mn^2+ ion, and the purple colour disappears if there is excess alkene. This means it can be used to differentiate between unsaturated and saturated hydrocarbons

Answer 97

Burn in excess oxygen to form CO2 and H2O. In air, they often don't burn completely and can produce a lot of CO or C, meaning the flame from alkenes is often quite sooty. The higher % of carbon in the hydrocarbon, the sootier the flame

Answer 98

Despite producing energy when they burn, they are not used as fuels as they are more important in the manufacture of polymers and other chemicals

Answer 99

When ethanol is treated with excess concentrated sulfuric acid (dehydrating agent) at 170°C, the alcohol loses water to form ethene

Answer 100

Concentrated sulfuric acid is also an oxidising agent (as well as a dehydrating agent) and so will oxidise some of the alcohol to CO2 and will be reduced to SO2. The acidic impurities are removed by passing the ethene through aqueous potassium hydroxide before collecting it over water.

Answer 101

Syrupy (concentrated) phosphoric acid can be used and does not undergo the side reactions of sulfuric acid (not an oxidising agent) but is more expensive than sulfuric acid

Answer 102

By soaking alcohol in rocksil/mineral wool and applying heat to a test tube also containing alumina or pumice stone (to provide a catalytic surface for the reaction), ethene vapour is produced which can be collected over water

Answer 103

If a halogenoalkane is treated with hot, concentrated potassium hydroxide solution in alcohol, it undergoes an elimination reaction to give an alkene, which is collected over water if it is a gas. The halogenoalkane loses the halogen atom and a hydrogen atom from a carbon atom next to the carbon atom with the halogen attached

Answer 104

Potassium hydroxide is usually dissolved in an alcohol containing the same number of carbon atoms as the halogenoalkane.

Answer 105

It would undergo a substitution reaction rather than an elimination reaction producing an alcohol

Answer 106

Iodoalkanes dehydrohalogenate more than bromoalkanes which dehydrohalogenate more easily then chloroalkanes. This is because there is a greater release of steric strain (how much space it takes up in a 3D space) for iodoalkanes Tertiary halogenoalkanes dehydrohalogenate faster than secondary and primary

Answer 107

Ethene and propene (in particular) are produced in huge amounts by cracking alkanes (heating them in the absence of air). Thermal cracking uses high temperatures of 500-600°C and catalytic cracking uses 400-500°C and a catalyst of chromium oxide, aluminium oxide or silicon oxide

Answer 108

When many molecules of a simple compound or 2 different compounds join together to form a molecule, this is called polymerisation, and the large molecule produced (from monomers) is the polymer

Answer 109

Alkenes undergo addition polymerisation, and the pi bond of the C=C bond breaks and the alkene molecules join onto each other. The polymer then has the same % composition and same empirical formula but higher Mr

Answer 110

- Polymer has a long life | - Not easily attacked by bacteria so good or outdoor use (e.g. guttering)

Answer 111

- If thrown away it stays in the environment for a long time - not biodegradable - Disposal by incineration gives toxic products of chlorine (e.g. HCl)

Answer 112

Polyethene (also known as polythene or polyethylene)

Answer 113

Polypropene (also known as polypropylene) - stronger than polyethene

Answer 114

Polychloroethene (also known as polyvinyl chlorine/ PVC)

Answer 115

Polytetrafluoroethene (also known as PTFE, fluon or teflon)

Answer 116

Polyphenylethene (also known as polystyrene)

Answer 117

Carbon dioxide is released into the atmosphere from burning fossil fuels to provide energy for production and transportation and incineration of polymers. There can be atmospheric pollution when incineration hasn't been carried out under the correct conditions. There are also landfill issues as most polymer products do not biodegrade so have to be disposed of in landfill. There can also be plastic pollution, and polymers can be found all over the world and have an environmental impact

Answer 118

Resistance to corrosion and chemical attack are useful properties, so give plastic products a long life

Answer 119

Discarded plastics can litter the environment (particularly smaller objects like plastic bags) and can fill waste disposal (more bulky plastic). If disposed of by incineration, especially of halogenated polymers, toxic fumes may be produced

Answer 120

- Not using them unnecessarily - Putting it to other uses > Recycling > Incineration > Use as chemical feedstock (raw materials)

Answer 121

Converting the polymer into other materials - e.g. PET/PETE from plastic bottles into carpet

Answer 122

1) Sorting - polymers cannot effectively be processed together, so there are codes that allow different polymers to be separated and sorted 2) Processing - Chopping the waste into small pieces and washing it. It can then be used to make new materials using melting, moulding and fibre production

Answer 123

Elements present in polymers are mostly H and C, so they can be used as fuels. There is very little solid waste left as most products of combustion are gases, and the energy produced can be used domestically and industrially.

Answer 124

As well as hydrogen and carbon, there are sometimes other elements, such as in colouring or small amounts of toxic heavy metals, which can cause air pollution as they are difficult to remove from waste gases released into the atmosphere

Answer 125

This is a process similar to cracking which is used to break polymer waste into gases (mainly carbon monoxide and hydrogen), which creates a chemical feedstock to use in other chemical reactions, often to make new polymers

Answer 126

- Main requirements for energy input - Environmental impact and sustainability of making materials from natural resources - Environmental impact of making the product from the material - Environmental impact of using the product - Environmental impact of disposing the product by incineration, landfill or recycling

Answer 127

To reduce the long term impact of a polymer on the environment and to compare different polymer uses, a life cycle analysis is drawn out

Answer 128

Biodegradable polymers are ones which are allowed to be broken down by microbes in the environment and are used on a small scale in medicine for stitches and drug delivery

Answer 129

They are often made from plant material, so land is required to grow the plants, and because they are designed to break down in the environment, the hydrogen and carbon atoms they contain cannot be directly used.

Answer 130

Small chains that join together in long chains to make polymers

Answer 131

Long chain molecules that are formed of many small molecules joined together

Answer 132

Proteins, polysaccharides, nucleic acids

Answer 133

Poly(eth)ene, polypropene, polystyrene, nylon, polyester

Answer 134

A process in which many small molecules (monomers) join up in long chains

Answer 135

It is able to break down in the environment due to the action of bacteria or microorganisms

Answer 136

A method of dealing with waste where a material is processed and reformed into new products

Answer 137

A waste management method where waste is dumped into large pits and covered with soil

Answer 138

The influence of any activity on the environment (atmosphere, sea, rivers, plants, animals)

Answer 139

Molecules or ions with a lone pair of electrons that they can donate to form new covalent bonds

Answer 140

Nucleophilic substitution, heat with aqueous KOH to form an alcohol (OH^- substitutes for the halogen ion)

Answer 141

Heat the halogenoalkane with aqueous AgNO3). Water replaces the halogen to form an alcohol and the halide ion is lost, and the halide ion will react with the silver nitrate to form a coloured ppt depending on the ion. Used to identify the halogenoalkane, not to produce alcohols

Answer 142

Heat the halogenoalkane under reflux with potassium cyanide in ethanol. This replaces the halogen with CN, adding an extra carbon to the chain

Answer 143

Heat the halogenoalkane in a high pressure sealed apparatus with concentrated ammonia in ethanol. The mechanism happens in 2 steps, first with NH3 joining onto the carbon that the halide ion was attached to, then because the N has too many bonds, then the lone pair on another NH3 removing the extra hydrogen, forming the primary amine and NH4^+

Answer 144

KOH in ethanol. Heat under reflux to form an alkene, the halide ion and water

Answer 145

Different halogenoalkanes undergo hydrolysis at different rates. The experiment is carried out by reacting different halogenoalkanes with aqueous silver nitrate in ethanol while heating in a water bath

Answer 146

Iodo reacts faster than bromo which reacts faster than chloro Tertiary reacts faster than secondary which reacts faster than primary

Answer 147

It has the longest bond (because of iodine's large atomic radius) so it has the weakest bond enthalpy and breaks the most easily of the halogenoalkanes. As bond lengths get shorter, bond enthalpy increases and they require more energy to break, which is why rate of hydrolysis decreases up the group

Answer 148

React via SN2. There are 2 species in the slow step (the nucleophile and the halogenoalkane) There is a 5-bonded transition state which has a negative charge. No carbocation is formed as the primary carbocations do not have sufficient inductive effects to stabilise the positive charge. The second step (kicking out the halide ion) is fast

Answer 149

React via SN1 There is 1 species in the slow step (the halogenoalkane) There is a carbocation intermediate A carbocation can be formed as the secondary and tertiary carbocations are made more stable by the inductive effects. The first step is slow and the second step is fast.

Answer 150

Clean blue flame when they burn in plentiful oxygen, carbon dioxide and water are formed

Answer 151

Vigorous reaction with PCl5 that forms steamy fumes (of HCl), POCl3 and a chloroalkane e.g. C2H5OH + PCl5 -> C2H5Cl + POCl3 + HCl This acts as a test for the hydroxyl group. The positive result of steamy is given when the HCl produced is exposed to ammonia

Answer 152

Heat under reflux with 50% (concentrated) sulfuric acid and KBr to produce a bromoalkane and water 2 stages, e.g. H2SO4 + 2KBr -> K2SO4 + 2HBr C2H5OH + HBr -> C2H5Br +H2O Halogenoalkane needs to be separated from reaction mixture

Answer 153

Heat under reflux with red phosphorus and iodine to produce an iodoalkane and H3PO4 2 stages, e.g. 2P + 3I2 -> 2PI3 3C2H5OH + PI3 -> 3C2H5I + H3PO4 Distill to separate halogenoalkane from reaction mixture as it has a low bp

Answer 154

Heat with potassium dichromate (VI) and dilute sulfuric acid | Product collected is an aldehyde as it has a low bp. A colour change from orange to dark green is seen (Cr^6+ to Cr^3+)

Answer 155

Heat with potassium dichromate (VI) and dilute sulfuric acid Product is fully oxidised to a carboxylic acid (aldehyde is formed first but it continues to be oxidised to a carboxylic acid). A colour change from orange to dark green is seen (Cr^6+ to Cr^3+). Carboxylic acid is purified using distillation as it has a much higher bp than the alcohol and alcohol

Answer 156

Heat under reflux with potassium dichromate (VI) and dilute sulfuric acid. Ketone produced. Orange to green colour change seen. Heating under reflux gives the best possible yield of the ketone, and the product is then purified and collected by distillation

Answer 157

No reaction with potassium dichromate (VI), so no colour change is seen

Answer 158

Use of Benedict's and Fehling's solution. They are both initially blue (due to Cu^2+ ions), and there is no reaction when added to a ketone, but a brick red ppt of copper (I) oxide is formed when added to an aldehyde

Organic Chemistry 1 - Alkanes to Alcohols Flashcards

(185 cards)