3.3: Organic chemistry Flashcards
(93 cards)
1
Q
What is IUPAC?
A
The International Union of Pure and
Applied Chemistry
2
Q
What are the prefixes based on the number of carbon atoms?
A
1: meth-
2: eth-
3: prop-
4: but-
5: pent-
6: hex-
7: hept-
8: oct-
9: non-
10: dec-
3
Q
What is the homologous series?
A
a series of related chemical compounds with the same R (functional group) but differ in formula by a fixed no. or group of atoms
4
Q
What is a functional group?
A
an atom/ group of atoms (e.g. carboxyl groups) that replaces H in an organic compound and defines structure of family of compounds, determining the family proteins
5
Q
What are the general functional groups of each homologous series?
A
- alkanes (-ane): R-CH3 or R-CH2-R1
- alkenes (-ene): R-HC=CH-R
- alcohol (-ol): R-OH
- aldehydes (-al): H-R=O
- kentones (-one): R-C(=O)-R
- carboxylic acid (-oic acid)
- halokane (chloro-,bromo-,iodo-,methyl-): R-I
6
Q
What are the IUPAC rules of alkane nomenclature?
A
- find and name the longest continuous carbon chain (with R group) a.k.a. parent chain
- identify and name groups attatched to the chain
- number the chains conscutively, starting at the end nearest a substituent group (lowest possible numbers!!)
- designate the location of each substituent group by an appropriate no. and name
- assemble the name, listing groups alphabetically, excluding no. stems
7
Q
What are the different formulas? e.g. butane
general, molecular, structural, displayed and skeletal
A
general- a chemical formula applicable to a series of compounds (e.g. CnH2n+2)
molecular- actual no. of atoms in a molecule (e.g. C4H10)
structural- the minimal detail that shows the arrangement of atoms in a molecule (e.g. CH3CH2CH2CH3)
displayed- the relative positioning of atoms and the bonds between them (e.g. H-C-C-C-C-H)
skeletal- the simplified organic formula, shown by removing hydrogen atoms from alkyl chains, leaving just a carbon skelenton and associated functional groups ( e.g. ^/
8
Q
What is an alkane?
A
- Alkanes are saturated hydrocarbons.
- alkanes consist of single carbon-carbon bonds
- The general formula for an alkane is CnH2n+2
- Except for alkanes in a ring structure, where it is CnH2n
- methane (CH4), is the most simple alkane
9
Q
What are properties of alkanes?
A
- Alkanes do not dissolve in water, as they are non polar (the electronegativity of carbon and hydrogen is similar).
- Because the water molecules are held together by H-bonds, and alkanes by VdW forces, they do not interact with each other.
10
Q
What is crude oil?
A
- Crude oil is often called a fossil fuel because it is made from the breakdown of organic matter, such as plants and animals.
- made up of dead plankton
- Crude oil is a non-renewable fuel as, although crude oil is being formed – it takes millions of years.
- Burning fossil fuels releases carbon dioxide – a greenhouse gas. Further more, impurities in the fossil fuels such as sulfur react with oxygen on combustion releasing sulfur dioxide.
11
Q
How does fractional distillation occur?
A
- Crude oil heated
- The mixture passes into a tower that is cooler at the top than the bottom
- The vapours pass up the tower via trays containing bubble caps until they arrive at a point that is cool enough to condense
- The mixture of liquids (fractions) are piped off at approximately similar chain lengths
- The shorter chain HCs condense nearer the top where it is cooler as they have lower forces of attraction and therefore lower boiling points
- The residue left at the bottom (bitumen) consists of very long chain HCs that are used as tar on roads
12
Q
Why does alkane cracking take place?
A
- Crude oil often contains a very high proportion of long chain hydrocarbons, these are less useful than then short chain hydrocarbons that we often associate with fuels.
- Cracking breaks longer hydrocarbons into a shorter alkane and an alkene.
-
Benefits of industrial cracking: Converts useless long chain alkanes to useful short chain alkanes, resulting in less waste, Creates ethene, an extremely useful precursor to making polyethene. This
can be sold for profit.
13
Q
What is a free radical?
A
Free radicals are highly reactive species
with and unpaired electron.
14
Q
What are the conditions and what occurs in thermal cracking?
A
- Conditions: Temp: 700-1200K, Pressure: 7000kPa
- Products: The carbon chain can break in any number of places, and hydrogen may be produced. This means that there is a high proportion of alkenes created.
- The covalent bond between 2 carbons splits equally, each carbon receiving and electron. These then go on to form a shorter alkane and an alkene. The conditions are intense so only maintained momentarily, usually around a second.
15
Q
What are the conditions and what occurs in catalytic cracking?
A
- Conditions: Temp: <720 Pressure: >1atm Zeolite catalyst
- Products: The products are also a mixture of alkanes and alkene, mainly of short chains (less than C=5), used in motor fuels. These are branched alkanes, cycloalkanes and aromatic compounds.
- Zeolite catalysts are honeycombed structure to give enormous surface area, they consist of silicon dioxide an aluminium oxide.
16
Q
How do you test for the presence of alkenes?
A
Bromine water
orange–> colourless if positive
17
Q
Differences between thermal and catalytic cracking?
A
Products:
It is a slight over-simplification but the zeolites used in catalytic cracking are chosen to give high percentages of hydrocarbons with between 5 and 10 carbon atoms - particularly useful for petrol (gasoline). It also produces high proportions of branched alkanes and aromatic hydrocarbons like benzene.
Thermal cracking gives mixtures of products containing high proportions of hydrocarbons with double bonds - alkenes
18
Q
Write an equation for the complete combustion of
methane
A
CH4(g) + 2O2(g) -> CO2(g) + H2O(l)
ΔH = -890 kJmol-1
- Alkanes are generally very unreactive, they wont react with acids,
bases, oxidising agents or reducing agents. However they are very
flammable and will react with halogens in the right conditions. - this reaction gives out a lot of energy. Hydrocarbons are used as fuels because they release a lot of heat on combustion. The more carbons present the more energy is released.
19
Q
What are impacts of burning fossil fuels?
A
- Burning fossil fuels pollutes the environment.
- Carbon dioxide is always given off when fossil fuels are burnt, it is an essential part of the earths atmosphere, however rising levels are causing an increase in the earths atmosphere and hence climate change.
- When hydrocarbons are burnt in a limited supply of oxygen, incomplete combustion occurs (generally longer chains).
- CH4(g) + 1.5O2(g) -> CO(g) + 2H2O(l)
- If even less oxygen is available, solid carbon may form.
- Carbon monoxide is a toxic gas and carbon particulates in the atmosphere can exacerbate asthma and are carcinogens.
20
Q
What are pollutants of alkane combustion?
A
Carbon monoxide (CO)- Produced during incomplete combustion of hydrocarbons, Toxic gas for humans.
Nitrous oxides (NOx)- The reaction between oxygen and nitrogen in the air, at the high temperatures of combustion, May react with water vapour and oxygen in the air to form nitric acid, a component of acid rain.
sulfur dioxide (SO2).- Formed when sulfur impurities in fossil fuels react with oxygen, May react with water vapour and oxygen in the air to form sulfuric acid, a component of acid rain.
Carbon particulates.- Incomplete combustion of hydrocarbons, Trigger asthma attacks in asthmatics and may cause cancer.
Unburnt hydrocarbons.- Evaporation from fuel, or non-combustion, Significant greenhouse gases and contributors to photochemical smog, which causes health problems.
Carbon dioxide (CO2)- Produced when fossil fuels are burnt, An important greenhouse gas, but in higher concentrations is a cause of
climate change.
Water vapour (H2O(l))- Naturally occurring, but increases with increasing temperature, A greenhouse gas.
21
Q
How to reduce pollutants (sulfur dioxide)?
A
- In many power stations, sulfur impurities is coal can react with oxygen to for sulfur dioxide.
- Calcium carbonate (or calcium oxide) can be sprayed on the flue gas to remove the sulfurous oxides.
- Reacting with lime wash is shown here, reacting lime (CaO) produces gypsum, a useful building material.
CaCO3(s) + 1.5O2(g) + SO2(g)-> CaSO4(s) + 2CO2(g)
22
Q
How to reduce pollutants (nitrous oxides)?
A
- Apart from sulfur, the internal combustion engine produces most of the pollutants that you have come across.
- IT is compulsory that all vehicles are fitted with catalytic converters to reduce nitrous oxide and carbon monoxide emissions.
2CO(g) + 2NO(g) N2(g) + 2CO2(g)
23
Q
What is the greenhouse effect?
A
- Like the glass in a greenhouse, gases in our atmosphere trap energy from the sun from leaving. This is important as it keeps our planet warm enough for life to survive.
- However, the earth is getting warmer, and the majority of scientists agree that is as a result of human production of carbon dioxide.
- Furthermore, as temperature increases, more water changes from the liquid state to a vapour, this exacerbates the effect of global warming. There is therefore a drive for us to reduce our emissions.
- Activities that do not release carbon dioxide overall, are called carbon neutral.
24
Q
What are halogenoalkanes?
A
- Halogenoalkanes are alkanes with one or more halogen groups.
- Halogenoalkanes can be formed by putting a mixture of an alkane and a halogen into bright light
- the UV light cause a reaction mechanism to occur resulting in a mixture of different halogenoalkanes forming.
CH4(g) + Cl2 (g)–>C6H13Br(g) + HBr(g)
25
What is free radical substitution?
These are reactions in which one hydrogen atom in a molecule is replaced by a halogen or group of atoms to produce a halogenoalkane.
- initiation: creates a free radical
- propogation: 2 steps that progress a reaction and end with a free radical
- termination: removes the free radical
26
# formation of halogenoalkanes
1.Initiation
| FRS
- The chlorine molecule absorbs a quantum of ultra violet light that is of enough energy to break the Cl-Cl single bond.
- The atoms are identical, so split evenly, each chlorine atom taking one electron from the bond. This is homolytic fission.
- This creates two chlorine free radicals. Often shown as Cl..
27
# formation of halogenoalkanes
2.Propogation
| FRS
This occurs is two stages:
- The chlorine free radical takes a hydrogen from methane, becoming stable hydrogen chlorine, creating a methyl free radical.
- Single headed curly arrows show the movement of a single electron.
- The methyl free radical is too, very reactive, so reacts with a chlorine molecule, generating another chlorine free radical.
- These steps occur thousands of times before the radicals are destroyed.
28
# formation of halogenoalkanes
3.Termination
- Termination is any reaction that removes free radicals:
- This may occur if two chlorine free radicals react with each other.
- Chain reactions are not actually a very useful method of producing halogenoalkanes. This is because a mixture of lots of different halogenoalkanes is formed.
- Longer chain alkanes may also produce many isomers of products as the chlorines can replaces any hydrogen on then chain.
29
What are halogenoalkanes?
Halogenoalkanes are much more reactive than alkanes. They have many uses, including as refrigerants, as solvents and in pharmaceuticals. The use of some halogenoalkanes has been restricted due to the effect of chlorofluorocarbons (CFCs) on the atmosphere.
30
What is bonding like in halogenoalkanes?
The electron pair in the carbon-halogen bond will be dragged towards the
halogen end, leaving the halogen slightly negative (δ-) and the carbon
slightly positive (δ+) - except in the carbon-iodine case.
Although the carbon-iodine bond doesn't have a permanent dipole, the bond is very easily polarised by anything approaching it.
31
What is a nucleophile?
A nucleophile is a species (an ion or a molecule) which is strongly attracted to a region of positive charge in something else.
Nucleophiles are either fully negative ions, or else have a strongly - charge somewhere on a molecule. Common nucleophiles are hydroxide ions, cyanide ions, water and ammonia.
- has at least one lone pair or negative charge
32
WHAT HAPPENS IN THE NUCLEOPHILIC SUBSTITUTION REACTIONS BETWEEN HALOGENOALKANES AND HYDROXIDE IONS (HYDROLYSIS)?
- The halogenoalkane is heated under reflux (heating with a condenser placed vertically in the flask to prevent loss of volatile substances from the mixture) with a solution of sodium or potassium hydroxide, the halogen is replaced by -OH and an alcohol is produced. Halogenoalkanes do not mix with water, so ethanol is used as a solvent. Water is present
- The reaction mechanism shows dipoles, curly arrows, charges and lone pairs
- nuclephile attacts carbon atom
- C-Halogen bond gos to Halogen
33
WHAT HAPPENS IN ELIMINATION REACTIONS BETWEEN HALOGENOALKANES AND HYDROXIDE IONS (ELIMINATION)?
- This is when a halogenoalkane is heated under reflux with a concentrated solution of sodium or potassium hydroxide in ethanol.
- In elimination reactions, the hydroxide ions have a very strong tendency to combine with hydrogen ions to make water in other words it acts as a
base - removing a hydrogen as a hydrogen ion from the carbon atom next door to the one holding the bromine. There is no water present.
- The OH- ion takes one of the hydrogens from the CH3 group, but it only needs the hydrogen nucleus (a hydrogen ion). That means that the two electrons which originally joined the hydrogen to the carbon aren't being used any more.
- Those two electrons (represented by a curly arrow) move to form a double bond between the two carbon atoms.
- The approach of those electrons repels the electrons in the carbon-bromine bond right out onto the bromine, throwing the bromine off as a negative ion.
- The attack could equally well have been on any of the other hydrogens on the left-hand carbon, or on any on the right-hand one - it simply depends on what the OH- ion hit.
34
What are CFCs and their uses?
CFCs stand for **chlorofluorocarbons**
Their uses included:
- Refrigerant coolants
- Blowing agents
- Solvents
- Aerosol propellants
35
Why do we use CFCs?
- CFCs were a non toxic replacement for ammonia in refrigerant fluids
- They were deemed safe as they were inert, not flammable, odourless and could be safely compressed
- Moreover, they are very cheap
- Also used as blowing agents, solvents and aerosol propellants
36
What is the issue with CFCs?
- CFCs remain unchanged in troposphere for decades, CFCs break down in the stratosphere
- UV rays cause CFCs to break down releasing chlorine radicals
- These radicals then collide with ozone and break down the ozone layer
- Chlorine radicals about 1000 x more likely than anything else to react with ozone
- One chlorine radical can deplete about 100,000 ozone molecules 1 million tonnes of CFCs put into atmosphere
37
What's happening to the ozone layer as a result of CFCs?
- A ‘hole’ in the ozone layer over the Antarctic was detected in the 1980s
- A technique that measures how strongly the atmosphere absorbs UV was used
- Less UV absorbed at the poles, indicating a thinning in the ozone layer
38
Why has the use of CFCs been banned in the UK since 1996?
- The C-Cl bond in a chlorofluorocarbon is broken by UV light. There is plenty of UV light in the atmosphere! The chlorine free radical produced acts as a catalyst in the destruction of ozone (O3).
Cl. + O3 -> ClO. + O2
ClO. + O3 -> Cl. + 2O2
2O3 -> 3O2
39
How to show mechanisms in an equation?
curly arrow- presents movement of pair of electrons
- arrow tail is where electron pair stats
- arrow head is where electron pair ends
- pair shown as bond, lone pair shown as pair of dots
- one electron shown through half arrow
40
What is an alkene?
a homologous series of unsaturatesd (at least one or more double C=C bonds) hydrocarbpns that share general formula CnH2n
41
What are the different bonds in alkenes?
SIGMA (o)- orbitals directly between bonding atoms/ orbitals overlap (1 overlap)
PI (π)- sideways overlap of adjacent p-orbitals above and below bonding carbon atoms (2 overlaps)
42
How do you draw s and p orbitals on a graph?
- x,y,z axis (perp. to each other)
- P orbital- infinity sign
- S orbital- sphere/ circle
43
What is the shape of alkenes?
- bond angles around C=C bonds are 120 degrees giving the mlecule a trigonal planar shape around C=C
- shape is determined by 3 electron domains, repelling equally
- π bonds resrict rotation of o bonds as they lie above and below the plane and the molecule
- if the o bonds rotates, the p bonds wouldnt align and overlap
44
What are the properties of alkenes?
- **alkenes are insoluble in water-** alkenes are non-polar molecules and water is polar so alkenes can only dissolve in non-polar substances
- **alkene boiling points increase with chain lengths-** longer chains have more points of contact, more induced dipole-dipole interactions (VDW forces)
- **alkenes have a lower b.p. than the equivalent alkane-** alkenes don't pack as well as alkanes due to change of shape around C=C bond, so there's fewer dipole-dipole forces. less electrons/ lower molecular mass, so fewer induced dipole-dipole interactions possible
45
Why are alkenes able to be attacked by electrophiles?
- Alkenes are susceptible to attack by electrophiles (lone pair acceptors).
- This is because the C=C double bond is very electron rich due to the electron cloud of the pi bond.
- In an addition reaction, the C=C double bond opens up and an atom or group of atoms joins onto each C of the C=C double bond.
46
What are Carbocation intermediates?
- During the reaction, a carbocation is formed as an intermediate species in the mechanism.
- Cations are positive ions (anions are negative ions). Positive ions with the positive charge on the C atom are called carbocations.
- Carbocations are very unstable as the C atom only has 6 electrons around it in the outer shell.
47
What do alkyl groups show about carbocation stability?
- In terms of stability, tertiary carbocations (which have three alkyl groups bonded to the C+ atom) are the most stable (or least unstable).
- tertiary (most stable), secondary, primary (least stable)
- Alkyl groups (e.g. methyl, ethyl, etc) are **electron-releasing** compared to hydrogen atoms (this is called the **inductive effect**). Therefore the more alkyl groups (rather than H atoms) on the C+ atom, the more stable the carbocation.
- This explains why in terms of stability **3y > 2y > 1y**
48
# W
What carbocation is most likely to form **if the alkene is unsymmetrial**?
- When alkenes undergo electrophilic addition reactions and different carbocations can be formed, the main product formed will be from the more stable carbocation intermediate (tertiary->secondary->primary)
- It is the structure and so stability of the carbocation intermediate that matters (not the structure / stability of the product).
- the most stable one forms as there is a **lower activation energy** to form the products so the most stable carbocation will be form the major product
- however, different products will always form as some particles may meet Ea
49
What is an electrophile?
- lone pair acceptor
- positively charged ions
- attack the electron dense C=C bonds
- polar molectules with delta positive region
50
What are the different forms of electrophillic addition?
- hydrogen halides (forms halogenoalkane)
- halogen (forms di-halogenoalkane)
- sulfuric acid (forms an alkyl hydrogen sulfate l w/ cold concentrated sulfuric acid catalyst)
- water (forms alcohol and strong acid catalyst)
51
What is the link between carbocations and products formed based on stabilty?
- tertiary most stable, primary least stable
- more stable, lower Ea, least positive
- less stable, higher Ea, more positive
- different products only form in unsymmetrical alkens
52
What is an addition polymer and how are they formed?
- formed from alkenes which can act as monomers and form polyners
- their double bonds ope up and join to make long chains
- these polymers are addition polymers, polyalkanes are saturated and non-polar so unreactive
| e.g. poly(phenylethene) -H2C-CH(benzene ring)-
53
What is the role of a plasticier?
WHAT?: makes polymer more flexible
- get between polymer chains and push them apart, reducing strength of VDW forces (i.m. forces) making them weaker
- allows them to slide around more so the polymer chain is easier to bend
54
What are propeties of polyalkanes?
- depend on im. forces
- usually non-polar so chains are only held together by VDW forces
- longer the polymer chains and the closer they can get, the stronger the VDW forces
- polyalkanes made up of **long, straight chains** tend to be **strong and rigid**
- polyalkanes made up of **short, branched chains** tend to be **weak and more flexible**
55
What is poly(chloroethene)/ PVC and its properties?
| H2C=CClH
- PVC has long, closly packed plymer chains
- his makes it hard but brittle at room temperature
**RIGID PVC:** drainpipes, windowframes
**PLASTICISED PVC:** used for tiles, clothing, cable insulation (as it's more flexible)
56
What is isomerism?
- an atom thst has the same **molecular** formula but atoms are arranged differently
2 types: structural isomerism and stereoisomerise
57
What is structural isomerism?
**molecules with the same molecular formula bt a diferet structural formula**
- **chain isomer-** caused by having a different carbon chain/ hydrocatbon chain arranged diferently
- **position isomer-** caused by functional group being in a different position/ attatched at different points
- **functional group isomer-** different functional groups
58
What is stereo isomerism?
**molecules with same molecular and structural formulas but a different arrangement of the atoms in the space**
- **E-Z isomers-** caysed by molecules with a C=C with 2 different groups attatched to each C of the C=C
- **optical isomers-** caused by C with atoms having 4 different groups attatched leading to molecules that are non superimposable mirror images of each other
59
What are CIP rules used for?
| Cahn, Ingold, Prelog
- these are used to assign stereoisomers as either E or Z
- this uses the atomic no. of the atom directly bonded to the C=C (double bond)
- E- ntgagen (opposite), Z-usammen (same)
same atoms on same side (top or bottom)
60
What are the CIP rules?
1. highest atomic numbers are diagonally opposite (E-isomer)
2. highest atomic numbers aren't diagonally opposite (Z-isomer)
3. if atomic no.s are equal, adjacent atoms are take into account (longer alkyl chains take priority)
61
What is an alcohol?
- a hydrocarbon chain with a functional -OH group
- made by the hydration of alkenes (addition of a water molecule)
- **CONDITIONS:** concentrated phosphoric acid catalyst, high temperature and pressure
- general formula: CnH2n+1OH -> **R**OH
62
What is the classification of alcohols?
- based on how many other R groups are bonded to the carbon with the -OH group
63
What is a Primary (1°) alcohol?
- carbon with -OH group has **1 R group**
- carbon has **2 hydrogen atoms**
- OH at the **end** of the chain
| **e.g. propan-1-ol**
64
What is a Secondary (2°) alcohol?
- carbon with -OH group has **2 R groups**
- carbon has **1 hydrogen atom**
- OH in the **body** of the chain
| **e.g. propan-2-ol**
65
What is a Tertiary (3°) alcohol?
- carbon with -OH group has **3 R groups**
- carbon has **0 hydrogen atoms**
- OH found on a **branch** of the chain
| **e.g. 2-methylpropan-2-ol**
66
What are the physical properties of alcohols?
- the -OH group means **hydrogen bonding** occurs between the molecules
- therefore alcohols have higher melting and boiling points than alkanes of similar relative molecular mass
- the -OH group can hydrogen bond to water molecules, whereas the non-polar hydrocarbon chain cannot
- hydrogen bonding predominates in short hydrocarbon chain alcohols making them soluble in water
- alkanes tend to have weaker intermolecuLar forces taking less energy to break (just **Van Der Waals**)
67
What are the uses of ethanol and methods of production?
**USES:** solvents in cosmetics, manufacture drugs, detergents, inks, coating
**PRODUCTION:** hydration of alkenes, fermentation
68
How are alcohols produced by the **hydration of alkenes**?
- with heat (steam) and acid catalyst (phosphoric)
- ethanol produced by the hydration of ethene by steam a 300C and a pressure of 60 atm
- non-renewable method
- 100% atom economy
- made in a batch
- H+ acts as electrophile
69
How is ethanol produced by **fermentation**?
- exothermic process carried out by yeast in anaerobic conditions (no oxygen)
- **C6H12O6-> 2CH5OH+2CO2 (+35C &yeast)**
- yeast produces an enzyme which converts sugars into ethanol and CO2
- once formed, ethanol is seperated by fractional distillation
- keep air out to prevent oxidation of ethanol to ethanoic acid
- 15% ethanol made
70
What is the process of fractional distilation of ethanol from fermentation?
1. turn on water, heat flask with bunsen burner causing water and ethanol vapours to be produced
2. vapours pass up fractionating column, water and ethanol seperate in column, water condenses back into flask in column
3. observe thermometer to keep the temperature at or below that of ethanol, only ethanol vapour (and little water passes into condenser, use condenser to cool vapours and condensse ethanol into a liquid
71
What is a biofuel?
**biofuel-** a fuel made from biological material that's recently died
72
What are advantages and disadvantages of biofuel compared to fossil fuels?
| made from sugars in sugar cane
**ADVANTAGES:** renewable & sustainable, carbon neutral
**DISADVANTAGES:** switching fossil fuels to biofuels means you have to change the car engine to get used to high conc. of ethanol, land used to grow crops for fuel can't be used to grow food
73
What does carbon-neutral mean?
the amount of CO2 released to the atmosphere when its burnt is equal to the amount of CO2 absorbed by the plant from which it was originally obtained
74
Why is ethanol production carbon-neutral (with equations)?
CO2 ABSORBED:
**photosynthesis:** 6H2O+6CO2 -> C6H12O6+6O2
6 moles total
CO2 RELEASED:
**fermentation:** C6H12O6 -> 2C2H5OH + 2CO2
**combustion:** 2C2H5OH + 6O2 -> 6H2O + 4CO2
2+4= 6 moles total
75
How is ethanol production not carbon neutral?
- carbon dioxide released in transport isn't factored in
- released in manufacturing
- production and distribution
- deforestation
- loss of biodiversity/ habitats
76
What is alcohol oxidation?
- burning alcohol or using oxidising agent acidified potassium dichromate (VI)/ K2Cr2O7 to mildly oxidise
**primary alcohol** -> aldehydes -> carboxylic acids
**secondary alcohol** -> ketones only
**tertiary alcohol** -> aren't pxidised
77
What are aldehydes, ketones and carboxylic acids?
**aldehydes:** have a **hydrogen and alkyl group** attatched to the **carbonyl (C=O)** carbon atom. suffix is **-al**, functional group always on C1
**ketones:** have **2 alkyl groups** attatched to **carbonyl (C=O)** suffix is **-one**. if there's more than 4 carbons, you have to say which carbon the carbonyl group is
**carboxylic acids:** have a **COOH (C=O & C-OH)** at the end of the carbon chain. suffix is **-oic acid**
78
What is the equation for the oxidation of primary alcohols into aldehydes and carboxylic acids?
**R-CH2-OH + [O] -> R-C=O-H +H2O**
**R-C=O-H + [O] -> R-COOH**
- [O]= oxidising agent
- gently heat ethanol with K2Cr2O7 and sulfuric acid producing ethanal (aldehyde)
- to just get the aldehyde, get it out the oxidising solution as soon as its formed using distillation apparatus so aldehyde (which boils at lower temp, than alcohol) is distilled immeditately
- to produce carboxylic acid, alcohol is vigorously oxidised w/ excess oxidising agent and heated under reflux
79
What is the equation for the oxidation of secondary alcohols into ketones?
**R1-CH/R2-OH + [O] -> (reflux) R1/R2-C=O + H2O**
- refluxing a secondary alcohol w/ acidified dichromate (VI)
- ketones aren't oxidised easily so prolonged reflux won't produce anything more
80
Why can't ketones be oxidised anymore from a secondary alcohol?
- aren't oxidised easily so prolonged reflux has no effect on ketone
- would require breaking of the C-C bonds
81
What happens when tertiary alcohols are oxidised?
- can't be oxidised
- don't react with potassium dichromate at all
- solution stays orange, only way to oxidise is by burning them
82
What is alcohol dehydration?
- the** elimination of a water molecule from an alcohol to form an alkene**
- allows you to produce alkenes from renewable rsources
- important as you can produce polymers poly(ethene) w/out needing oil
- one of the main industrial uses for alkenes is a starting material for polymers
- **ethanol heated w/ a conc. sulfuric acid catalyst or phosphoric acid**
- product is usually a mix of water, acid and reactant where alkene is seperated from
- dehydrating unsymmetrical alcohols produces ore products
**CnH2n+1 -> CnH2n + H2O**
83
What is the difference between distillation and reflux?
**distillation-** the seperation of different substances in a solution with different boiling points
**reflux-** the same solution is condensed into the same flask.
84
How do you test for haloalkanes (R-X)?
1. add NaOH and warm
2. forms halide in solution
3. acidify w/ nitric acid
4. add silver nitrate
FORMS PRECIPITATE
Cl- white ppt
Br- cream ppt
I- yellow ppt
85
How do you test for alkenes (C=C)?
add bromine water, mix
goes orange -> colourless
86
How do you test for an alcohol (R-OH)?
- add sodium/ potassium dichromate (Na2Cr2O7/ K2Cr2O7) acidified by sulfuric acid (H2SO4)
**primary and secondary alcohols** go from orange to green
**tertiary alcohols** have no change in colour
87
How do you test for an aldehyde and a ketone (R-C=O)?
1. add Fehling's solution or Tolan's reagent
2. heat
**F**- in aldehyde, it goes **blue -> red**, in a ketone nothing happens
**T**- in aldehyde, it goes **silver mirror**, in a ketone nothing happens
88
How do you test for a carboxylic acid (R-COOH)?
1. add any carbonate e.g. NaC
2. bubble gas through limewater
turns bubbly/ cloudy and forms white ppt
89
How can Time of flight mass spectrometry be used in organic analysis?
- find **abundance and mass** of each isotope in an element to find the atomic mass
- find **relative molecular mass** of substances made of molecules
- molecular ion formed creating **a molecular ion peak** on the mass spectrum of the compound
- mass:charge (m/z) value is similar to molecular mass
1. ionisation (electron impact/ electrospray)
2. acceleration
3. flight tube
4. deceleration
90
How can High resolution Time of flight mass spectrometry be used in organic analysis?
- can measure extremely accurate high resolution mass spectrometers
- can be useful for identifying compounds that appear to have the same Mr when rounded
91
How can infared spectrometry be used in organic analysis?
- this is a **beam of IR radiation** is passed through a sample of a chemical
- the IR radiation is absorbed by the covalent bonds in the molecules, increasing the vibrational energy
- bonds between different atoms absorb different **frequencies of IR radiation**
- helping to **identify functional groups**
-
92
What is the fingerprint region?
- the region between 500 and 1500 is called the fingerprint region
- unique to a particular compound
- this is checked using a computer database
93
How is infared radiation absorption linked to global warming?
- some of the em radiation emitted by the sun reaches the earth and is absorbed, the earth then re-emits some pf it as infared radiation (heat)
- molecules if greenhouse gases absorb the IR. they reemit some of it back towards us to kep the earth warm **greenhouse effect**
- human activities such as burning fossil fuels and leaving rubbish to rot in landfill sites, have caused a rise in greenhouse gas concentrations
- this means heat is being trapped and the earth is getting warmer **(global warming)**
