7 Organic chemistry Flashcards
1
Q
formuala for alkanes
A
CnH2n+2
2
Q
what does saturated hydrocarbon mean
A
contains no carbon-to-carbon double bonds, only single bonds
3
Q
properties of short hydrocarbons
A
- the shorter the carbon chain the less vicous it is
- the shorter carbon chain the more volatile they are - lower boiling point
- the shorter the more flamable
opposite for longer hydrocarbons
4
Q
complete combustion
A
- happens when burning a staurated hydrocarbon eg. alkane and alcohol
- saturated hydrocarbon + oxygen —> carbon dioxide + water
5
Q
what is crude oil
A
- fossil fuel
- made from plants and animals that died million years ago - over this period high tmep and pressure turned reamians to crude oiil
- drilled up from the rocks where it’s found
- non-renweable fuels
6
Q
why do we use fractional distilation
A
- to seperate the different compunds in crude oil
- each hydrocarbon length has different uses
7
Q
how do fractional distillation columns work
A
- oil is heated until most of it turns into a gas
- gas enters the fractionating column
- in the column there is a temperature gradient- hot at bottom cooler as you go up
- the longer hydrocarbons with higher boiling points condense back into liquids and drain out the column near the bottom
- shorter hydrocarbons have lower boiling points so condense much later on near the top of the column where its cooler
- end up with crude oil misture seperated out into different fractions
- each fraction contains a mixture of hydrocarbons that contain similiar number of carbon atoms so have similiar boiling points
8
Q
hydrocarbon uses and their lengths
A
- very short - petroluem gas
- short - petrol
- somewhat long - kerosene
- long - diesiel oil
- very long - heavy fuel oil
9
Q
what is a homolgous series
A
- a family of hydrocarbons with similar chemical properties who share the same general formula
- eg, alkanes, alkenes, alcohols, carboxylic acids
10
Q
what is cracking
A
- splitting up long-chain hydrocarbons into smaller ones
- thermal decompostion reaction - breaking molecules down by heating them
11
Q
why do we do cracking
A
- long-chain hydrocarbons aren’t very useful
- however short-chain hydrocarbons are useful since they’re flamable so make good fuels and are highly in demand
12
Q
products of cracking
A
long-chain hydrocarbon —> short-chain hydrocarbon + alkene
13
Q
how do you crack a hydrocarbon
A
- heat long chain hydrocarbons to vaporsie them
- the vapour is passed over a hot powdered aluminium oxide catalyst
- long-chain molecules split apart on the surface of catalyst - catalytic cracking
- can also crack them by after vaporising mixing with steam and then heating to a very high temp - steam cracking
14
Q
what is an alkene
A
- hydrocarbon with a double C=C bond
- CnH2n
15
Q
what is an unsaturated hydrocarbon
A
contains carbon-to-carbon double bonds
16
Q
incomplete combustion
A
- happens when burning alkenes
alkene + oxygen —> carbon + carbon monixide + cabron dioixde + water
17
Q
how do alkenes react
A
- via addition reactions
- the C=C opens up to leve a single bond and a new atom is added to each cabrons
18
Q
what happens when you react a hydrogen and alkene
A
- hydrogenation
- hydrogen opens up the double bond and forms an equivelant, saturated alkane
- eg:
R H…………………….. H H
C=C + H2 —> R - C - C - H
H H …………………… H H
r - hydrocarbon
19
Q
what happens when steam is added to alkenes
A
- forms alcohol
- ethene is mixed with steam forming ethanol
industrial making: - after reaction takes place, mixture passed from reactor to condenser
- ethanol and water have higher boling points than ethene so both condense whilst unreacted gas ethene is recycled back to the reactor
- alcohol is then purified by fractional distilation
20
Q
what happens when you add a halogen to an alkene
A
- halogens break C=C bond
- each C=C bond becomes bonded to a halogen atom
- eg.
H H…………………….. H Br
C=C + Br2 —> H - C - C - H
H H …………………… Br H
21
Q
describe what happens when you add bromine to alkenes
A
- when orange bromine water is added to alkene the bromine will add accross the double bond making a colourless dibromo-compound
- so bromine water decolourised
22
Q
whats a functional group
A
goup of atoms that determines how that molecule typically reacts
- alkane - C=C
- alcohol - OH
- Carboxylic acids - COOH
- Ester -COO-
23
Q
what are polymers
A
- long molecuels formed when lots of small molecules called monomers join
- usually carbon based
- monomers often alkenes
24
Q
how to draw polymers
A
- n infornt of bracket with double bond inside - write type of monomer
- in bracket single bond, bonds drawn extending out of brackets with n after the bracket - write poly(type of monomer)
25
how to write an alcohol formula
with OH to show functional group
eg. not CH4O instead CH3OH
26
porperties of first 4 alcohols
- flammable, undergo complete combustion in air
- all soluble in water
- have a neutral pH
- react with sodium - one product is hydrogen
- can be oxidised to produce carboxylic acid
- different alcohols form diff carboxylic acids
27
uses of alcohols
- used as solvents, can dissolve most things including things water can and can't
- used as fuels
- alcoholic drinks
28
how else can ethanol be made
- through fermentation
- used in alcoholic drinks
sugar ---> ethanol + carbon dioxide
- happens at 37 degrees, slightly acidic and anaerobic conditions
29
carboxylic acid properties
- names end in "-anoic acid"
- react with carbonates to produce salts, water and CO2
- salts formed end with -anoate
- dissolve in water, ionise releasing H+ ions forming acidic solution, don't completely ionise so form weak acid solution, have higher pH
30
how are esters formed
- formed from alochols and carboxylic acids
- alcohol + carboxylic acid ---> ester + water
31
what are esters
- organic compounds , functional group -COO-
- Esters have fruity smells and can be used as solvents and perfumes
32
what is condensation polmeristaion
- involves monomers with different fucntional groups
- react making polymer chains between them
- for each new bond a smaller molecule is created eg. water
33
addition vs condenstaion polymeristaion no. of types of monomers
- Add. - only **one** monomer containg **C=C**
- Con. - **2** monomer types containing **2** of the **same** **functional** groups OR **one** monomer type with **2 different functional** groups
34
addition vs condenstaion polymeristaion no. of products
- Add. - one product formes
- Con. - 2 products form - polymer and small molecule eg. water
35
addition vs condenstaion polymerisation functional groups involved
- Add. - C=C bond in monomer
- Con. - 2 reactive groups on each monomer
36
naturally occuring polymers
- amino acids
- protiens, polymers of amino acids
- DNA - made from nucelotide polymers
- simple sugars from polymers
37
amino acid functional group
- basic amino group NH2
- acidic carboxyl group COOH
38
how are proteins formed
- amino acids form polymers - polypeptides through condenstaion poylmeristaion
- amino group of an amino acids reacts with acidic groups of others to form a polymer chain, for every new bond water is lost
- one or more long-chains of polypeptides are protiens
- polypeptides and proteins that can contain different amino acids in their polymer chains
- order of amino acids is what gives protiens their properties and shapes
39
what is DNA made from
- made of 2 polymer chains of monomers called nucleotides - contain a small molecule, a base - ACGT
- bases on different polymer chains pair up with each other and form cross links keeps the 2 strands of nucelotide strands together
- order of bases acts as a code for an organism's genes
40
how do simple sugars form polymers
- sugars are small molecules containing carbon, oxygen and hydrogen
- can react together through polymeristaion reactions to form larger carbohydrate polymers eg. starch - store of energy and cellulose - use in plant cell walls
