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Organic Chemistry Flashcards

1
Q
A
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2
Q

What does saturated mean?

A

Contains single carbon bonds only

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3
Q

What does unsaturated mean?

A

Contains a C=C double bond

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4
Q

What is steroisomerism?

A

Molecules with the same structural formulae but have different spatial arrangments of atoms

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5
Q

How do you class which atom is the priority group

A

The atom with the bigger atomic number

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6
Q

When do E Z isomers arise?

A

When there is restricted rotation around the C=C double bond
and when there are two different groups/isomers attached to both ends of the double bond

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7
Q

How do you identify an Aldehyde and what does its name end in?

A

It always has a C=O bonf on the first carbon chain so it does not need a number only di or tri. Its name ends in -al.

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8
Q

How do you identify ketones and what is their suffix?

A

Ketones have 5 carbons or more in a chain then it needs a number to show position, if not it dosent need one. Ketones have double carbon bonded to oxygen on any but the first carbon. Its suffix is -one

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9
Q

How do you identify carboxylix acids in stuctural formulae and what is their suffix?

A

No number neccesary for this group as it must always be at the end of the chain. It consists of an -OH group and double bond of oxygen attached to the same carbon at the end ends in oic acid

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10
Q

When is the hydrox- prefix used?

A

When aldehydes and alchohols are in the same molecule, aldehydes take higher priority than alchohols and so the al suffix is used whereas hyrox prefix is used, e.g. 4-hydroxylbunanal

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11
Q

Describe the process of fractional distillation

A

Oil is pre-heated then passed into column.
The fractions condense at different heights
The temperature of column decreases upwards
The separation depends on boiling point.
Boiling point depends on size of molecules.
The larger the molecule the larger the London forces Similar molecules (size, bp, mass) condense together Small molecules condense at the top at lower temperatures
big molecules condense at the bottom at higher temperatures.

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12
Q

What is cracking?

A

The conversion of large hydrocarbons to smaller molecules by breaking c-c bonds in thermal decomposition +the production of hydrogen

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13
Q

Describe the economic reason for catalytic cracking

A

-Shorter chain molecules are more in demand
- Makes use of excess larger hydrocarbons to supply demand for shorter
-Products of cracking are more useful as materials and used as fuel

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14
Q

Why does cracking require high temperatures?

A

It is a chemical process that nvolves splitting of strong covalent bonds and so requires high temperatures

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15
Q

What does reforming do?

A

Turns straight chain alkanes into branched and cyclic alkanes and aromatic hydrocarbons

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16
Q

Explain why alkanes are used as fuels?

A

They readily burn in the prescence of oxygen, This combustion of alkanes is highly exothermic

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17
Q

What would be the physical observation that incomplete combustion has occured?

A

A sooty flame would be produced

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18
Q

Describe the properties of CO and how it is dangerous to humans

A

CO is a colourless gas that is toxic to gumans as it can form a strong bond with haemoglobin in red blood cells. This is a stronger bond than made with oxygen s it prevents oxygen attaching to the haemoglobin

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19
Q

What bonds does the double covalent bond in alkenes consist of?

A

One sigma (o) bond and One Pi bond (π)

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20
Q

Describe makes double covalent bond in an alkene so vunerable to attack by electrophiles

A

The double covalent bond consists of exposed Pi bonds either side of the bond, Pi bonds have high electron denity makeing them more vunerable to attack

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21
Q

Describe how a sigma bond is formed and the movement around the bond

A

One sp (squared) orbiatal from each carbon overlap to form a single c-c bond called sigma. Rotation can occur around the bond

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22
Q

Describe the formation of a pi bond ,how it results in it being more subseptible to attack by electophiles, its strength in comparison to the sigma bond and rotation around the bond

A

The Pi bond is formed by sideways overlap of two P orbiatals on each carbon atom. This forms a Pi bond above and below the plane of the molecule. Because Pi bonds have high electron density, theis leaves bond with high electron density above and below line between two nucleui so eletrophiles are attracted. It sis weaker than the sigma bond and there is restricted rotation aroud the bond

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23
Q

What is an addition reaction?

A

When two molecules reacts to produce 1

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24
Q

Describe the reagent, condition and type of reaction used to turn an alkene into an alkane

A

Reagent- Hydrogen
Conditions- Nickel catalyst
Type of reaction- Addition/reduction

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25
Describe what is formed from the reaction of alkenes with bromine/chlorine and the reagent used, conditions, mechanism and type of bond fission
Formed- Dihalegenoalkane Reagent- Halogen reagent dissolved in organic solvent Conditions- Room temperature, No UV light Mechanism- Electrophilic addition Bond fission- heterolytic
26
Describe the reaction of hydrogen bromide with alkenes including what type of molecule is formed, the reagent used, the conditions, the type of mecahnism and the type of bond fission
Formed- Halegenoalkane Reagent used- HCL or HBR (H+ electrophile) Conditions- Room temperature Type of mechanism- Electrophillic addition Type of bond fission- Heterolytic
27
Describe happens as Br2 approaches the alkene molecule to produce carbocation
The Pi bonds in the electrons reject the electron pair in Br-Br, this induces a dipole making Br2 polar and electrophillic.
28
Explain why teriary rather than secondary and secondary rather than primary carbocations are more stable than
Because the methyl groups on either side or one side of the positive carbon formed after first bromie/chlorine molecule produces the carbo cation are electreon releasing, reducing the charge on the ion therefore making it more stable.
29
Describe the reagent,condition,reaction and its observations of an alkene forming a diol diol
Cold KMnO4 in acidified solution at room temperature is added to the alkene which undergoes an oxidation reaction. The purple colour of MnO4 ion is changed from purple to colourless.
30
Write out the displayed formula of propene reacting to become a diol and name the diol
31
What is a radical and how is it formed?
It is a species with unpaired electrons that is formed by homolytic fission of a covalent bond and results in the formstion of radicals
32
Describe another test for alkenes that dosent involve diols
Bromine dissolved in water at room temperature undergoes an addition reaction with alkenes . The porange colour of bromine water will decolourise to colourless
33
Describe how alkenes form alchohols
They undergo hydration reaction with water in the precence of the acid catalyst- H3PO4 (phosphoric acid) under high temperature(300-600") and high pressure of 7atm
34
Why is the formation of alkenes to alchohols easy and cheap to carry out industially?
There are no waste products and in additon the reaction has a high atom economy
35
Why are Poly (alkenes) and alkanes unreactive?
The have strond C-C and C-H bonds
36
Comapre the properties and uses of polyethene and polypropene
Polyethene - Flexible, easily molded, low density and waterproof so used for plastic bags Polypropene- Stiff and Higher density- Used as platic containers/ untensils
37
Describe and evaluate the 3 different methods of disposing of waste polymers
Incineration- Rubbish is burnt and energy is used to generate energy. Toxins released from combustion and Halogenated platics can form HCL gas which is toxic, however this can be reacted with a base or carbonate and neutraised before released in the atmosphere Modern incinerators can burn more efficiently removing tocins and products but greenhouse gases still released Recycling- Saves raw materials as most polymers formed from crude oil. A lot of man power/ energy into sorting and collecting as only same type of polymer recylcled as 1. Thermo plastics can be melted and reshaped. Feedstock- Polymers can be cracked into small molecules whcih can be used to ake other new polymers saving raw material.
38
What substances have scientist made biodegradable and compostable polymers from?
Maize and Starch
39
Describe the differnece between Primary, Seconary and tertiary halogenoalkanes
Primary 1, Secondary 2 and tertiary 3 carbons attached to the carbon adjoining the halogen
40
What two reactions dop halogenoalkanes undergo?
Elimination or substitution
41
What is a nucleophile and list the ones used in reactions with Halegenoalkanes
An electron pair donator - :CN-, :NH3, :OH
42
List the order in which the speed of substitution reaction happens between C-X bond (X being the hallide ions) and explain why
Fastest-- C-I C-Br C-Cl C-F This is the order because of the bond enthalpies of these molecules, C-F, has very high bond enthalpy and so it very unreactive buy C-I has lowe bond enthalpy and is more reactive so reacts faster
43
Explain why a precipitate forms in the hydrolysis of halegenoalkanes
Hydrolusis by water releases a hallide ion which reacts with silever ion to form an insoluble silver hallide precipitate
44
Describe the process and conditions under which a halgenoalkane forms an alchohol
The nucleophillic substitiution of halegenoalakne with aqueous hydroxide ions (KOH or NAOH) in aqueous solution under heat reflux reacts to form an alchohol, tertiary and primary halegenoalkanes react in different ways
45
Why is OH- a stronger nucleophile than water?
It has full negative charge and so its more strongly attracted to the slightly positive carbon
46
What is the importance of aqueous conditions in reaction that turns halegonalkane to an alchohol?
If its solvent is changed to ethanol, elimination reaction occurs rather than substitution.
47
Draw the mechanism for reaction of bromoethane (primary carbocation) with OH-
48
In what way do tertiary halogenoalkanes undergo nucleophilic substitution mehanism differently from primary and why?
The hallide ion breaks away from the halegenoalkane to form carbocation intermediatte. The hydroxide ion then attacks the positve carbon rather than the OH- attcking positive carbon and then bond between bromine and carbon breaking. This is because there are methyl groups either side of the positive carbon which stabilise it as they release electrons. In addition the bulky methyk groups prevents direct attack of OH- on halogenoalkane the same way it does for primary
49
Describe how halegenoalkanes form amine groups
Through nucleophillic substitution with ammonia dissolved in methanol where :NH3 is the nucleophile. Reaction occurs under pressure in a sealed container.
50
Why would excess ammonia be used in the reaction between halegenoalkane and ammonia?
The amine group formed and halegenoalkane can continue to undergo futher substitution leading to a lower yield of the amine product, excess ammonia minimises this
51
Describe the reaction that forms an alkene from a halogenoalkane
ELimination reaction with NaOH or KOH in ethanol under heat
52
How do you know if a reaction with a halogenoalkane and KOH or NaOH is an elimiation or substitution reaction
Substitution reaction- Hydroxides are in aqueous conditions Elimination reaction- Hydroxides are in alchoholic condition (in ehtanol)
53
What effect does the structure of halegenoalkanes have on the degree to which substitution or elimination occurs?
Primary halogenoalkanes tend towards substitution whereas, Tertiary Halogenoalkanes tend towards elimination
54
What are the observations of alchohol reacting with sodium?
Gas bubbles Mixture gets Hot Sodium dissolves WHite solid produced
55
Name 4 halogenating compounds thta can substitute -OH group in alchohol to form a halegeno alkane
Conc HCL NaCl & H2SO4 PCl5 PCl3
56
How would you test for an alchohol using PCl5?
When added misty fumes of HCL will be observed
57
How do you produce bromo alkanes from alchohols?
50% conc sulfuric acid and Potassium bromide
58
How would you produce iodo alkanes from alchohols?
Red phosphorus and iodine
59
Hpw do you produce chloro alkanes from alchohols?
Add PCl5
60
What oxidising agent is used to oxidise alchohols?
Potassium dichromate (K2Cr2O7)
61
Describe the partial oxidation of a primary alchohol including what is formed, the reagents used and the conditioms under which reaction takes place
Formed- Aldehyde and water molecule Reagent-Potassium dichromate(VI) solution and dilute H2SO4 Conditions- Using limited amount of dichromate and distilling out aldehyde as it forms
62
Draw the displayed formula equation for for the oxiudation of propan-1-ol into propanal
63
Describe the full oxidation of primary alchohols includiong what is produced, reagents used and conditions
Products- Carboxylic acid and water Reagent- Potassium dichromate and dilute H2SO4 Conditions-Excess dichromate and heat under reflux, distil off product only after reaction has finished
64
Descrieb what would be observed in the full oxidation of a primary alchohol
The orange dichromate ion (Cr2O7 2-) reduces to the green Cr 3+ ion
65
Draw structural formuale of the full oxidation of propan 1 ol
66
Desribe oxidation of secondary alchohols including what is formed, Reagents used and the conditions
formed- Ketone and water Reagents Pottasium dichromate and dilut H2SO4 Conditions- Heated under reflux
67
Draw the displayed fromuls reaction of oxidised propan 2 ol
68
Describe the observations of a secondary alchohol being oxidised
The dichromate ion (Cr2O7 2+) which is an orange solution is oxidised to produce Cr 3+ which is green
69
Why can tertiary alchohols not be oxidised at all by potassium dichromate?
There are no hydrogen atoms attched to the carbon with the OH group
70
What fact is the chemical basis for test to distinguish aldehydes and ketones?
Aldehydes can be futher oxidised to produce carboxylic acids but ketones cannot
71
Describe the test to distinguish aldehydes and ketones
Alchohol is gently heated with fehling bendicts solution which contains Cu2+ ions The aldehydes are oxidised by benedicts solution into a craboxylic acid and the copper (II) ions are reduced to copper (I) oxide. Blue Cu 2+ ions in the solution change to a red precipitate of Cu2O. Ketones dont react
72
How can the presence of carboxylic acids be tested?
Addition of sodium carbonate will show fizzing and produce carbon dioxide
73
What is a dehydration reaction?
Removal of a water molecule from a molecule
74
Decribe the test to turn an alchohol into a alkene including the reagent, conditions, role of reagent and the the type of reaction
Reagent- Phosphoric acid Conditions- warm under reflux Role of reagent- Dehydrating agent/ catalyst Type of reaction- Acid catalysed elimination
75
What are the products of an alchohol undergone dehydration reaction?
Alkene and Water Molecule
76
Draw and lab;e the distillation apparatus using labels: Themometer, Heat, Liebig condenser, Water in& Water out
77
How do you provide stronger oxidisng conditions in a distillation apparatues for alchohols to carboxylic acids?
Remover themometer, Place condeser directly on top of the flask in vertical position
78
What is a reflux reaction?
When organic mixtures are heated for long periods of time and the condenser prevents organic vapours from escaping by condensing them back to liquids
79
Why should the end of the condeser when heating volatile liquids never sealed?
A build up of gas pressure can cause the apparatus to explode
80
Why are anti-bumping granules added to the flask in both distillation and reflux?
To prevent vigorous uneven boiling by making small bubbles instead of large bubbles
81
Draw the apparatus of a reflux reaction using lables: Heat, round bottomed flask, water in, water out, condenser
82
What are electric heaters often used to heat organic chemicals alternative to flame
organic chemicals are usually highly flammable and could set fire with a naked flame
83
Name the 5 pollutants and their impact on the environment
Nitrogen oxides- NO is toxic and can form smog NO2 is toxic and acidic it forms acid rain Carbon monoxide- toxic Carbon dioxide- Contributes towards global warming Unburnt hydrocarbons-Contirbutes to the formation of smog Soot/particles- Global dimming and respiratory problems
84
Catalyic converers have cermaic honeycomb coated with a thin layer of catalyst metals, Give examples of these ,metals and why they are there?
Platinum, palladium, rhodium To give a large surface area

Chemistry (7 decks)

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