Organic Chemstry I- Topic 6 Flashcards
What is a homologous series?
A group of organic compounds that have the same functional group and general formula.
What do consecutive members of a homologous series differ by?
CH2
Define Addition
Joining two or more molecules together to form a larger molecule
Define Polymerisation
joining together
Elimination
When a small group of atoms breaks away from a larger molecule
Substitution
when one species is replaced by another
Hydrolysis
splitting a molecule into two new molecules by adding H+ and OH- derived from water
Oxidation
Any reaction in which a species loses electrons
Reduction
Any reaction in which a species gains electrons
When naming organic molecules, which functional group is most important and how does this affect its name?
The double bond so it should be given the LOWEST number when naming it.
What does the 1 in butan-1-ol tell you and why is it necessary in the name?
Tells you that the functional group is attached to the 1st Carbon. This is necessary as different molecules such as butan-2-ol exist.
What is the displayed formula?
When you draw out all bonds etc like C=C-H ….
What is the structural formula?
Showing the arrangement of atoms carbon by carbon
Ch3Ch2Ch3
What is the molecular formula?
The actual number of atoms of each element in a molecule e.g. C2H6
What is a mechanism?
A diagram that breaks down reactions into individual stages to show how substances react together.
What do curly arrows show?
How electron pairs move around when bonds are made or broken.
What is a hydrocarbon?
A compound consisting of ONLY hydrogen and carbon
What does saturated mean?
Containing single carbon-carbon bonds only
What does unsaturated mean?
Contains a C=C double bond
What is a general formula?
Algebraic formula that can describe any member of a family of compounds.
The shape around the carbon atom in saturated hydrocarbons is ………. and the bond angle is ……
The shape around the carbon atom in saturated hydrocarbons is tetrahedral and the bond angle is 109.5
What are the only things skeletal formulas show?
a carbon skeleton and any functional groups.
What is a functional group?
An atom or group of atoms which (when presented in different molecules) causes them to have similar chemical properties.
If more than one double bond is present then the suffix will end in…… or …..
diene or triene.
What will you name a compound that has OH and a higher priority functional group?
name using “hydroxy”
e.g. hydroxypropanoic acid
What is a structural isomer?
same molecular formula but different structural formula
What is a chain isomer?
Compounds with the same molecular formula but different structures of the carbon skeleton.
What is a position isomer?
Compounds with the same molecular formula but different structures due to different positions of the same functional group on the same carbon skeleton.
What is a functional group isomer?
Compounds with the same molecular formula but with atoms arranged to give different functional groups.
What is a nucleophile?
An electron pair donor. (often negatively charged ions e.g. halide ions) or species with a lone pair.
Molecules with …… ..… are often attacked by nucleophiles
Molecules with polar bonds are often attacked by nucleophiles
What is an electrophile?
An electron pair acceptor, often positively charged ions.
Name 3 types of reagent
Electrophile
Nucleophile
Radical
Radicals have ….. ……….
Radicals have unpaired electrons
When naming organic molecules, what must you remember when knowing which side chains have priority?
Alphabetical order. So the Methyl comes before the Propyl.
Which alkanes have the highest boiling points?
Straight chain alkanes have the highest boiling points, and are higher than branched chain alkanes due to the greater surface area in contact.
Why do hydrocarbons have a low affinity (unreactive)?
Hydrocarbons have NO significant dipole in C-H and C-C
Each fraction (crude oil) contains a ………. of hydrocarbons
Each fraction (crude oil) contains a mixture of hydrocarbons
What is breaking a covalent bond called?
Bond Fission
What are Heterolytic and Homolytic Fission examples of?
The two different ways that a single covalent bond between two atoms can break.
What is heterolytic fission?
The bond breaks unevenly with one of the bonded atoms receiving both electrons from the bonded pair. Therefore two substances can form, an anion and a cation.
What is homolytic fission?
The bond breaks evenly, each atom receives 1 electron. Two “radicals” are formed.
What happens in the initiation step?
Radicals are produced
What happens during the propagation step?
Radicals are used up and created in a chain reaction.
What happens during the termination step?
Radicals mopped up by reacting together and forming stable molecules.
What’s the general formula for alkanes?
CnH2n+2
What is nomenclature?
The system used for naming organic compounds.
Give the suffixes for:
Aldehyde
Ketone
Carboxylic acid
Aldehyde- al
Ketone- one
Carboxylic acid- oic acid
What are stereoisomers?
Organic compounds with the same molecular formula but have different arrangements of atoms in space.
E-Z isomerism is caused by…..
the limited rotation about C=C double bonds.
How are E and Z isomers differentiated?
Two substituents with the HIGHEST MOLECULAR MASSES:
Z = both on same side
E = both on opposite sides.
What is cis-trans isomerism?
Two substituents on each carbon atom are the same.
Each fraction (in crude oil) contains a ….. of ………..
Each fraction (in crude oil) contains a mixture of hydrocarbons.
Which alkanes have the highest boiling points and why?
Straight chain alkanes have the higher boiling points (more than branched chain alkanes) due to the greater surface area in contact.
What is a reagent?
A substance added to a system to cause a chemical reaction, or added to test if a reaction occurs.
What is a free radical?
an atom with an unpaired electron.
What is carbocation?
A carbon atom bearing a positive charge
What is a pi orbital formed from?
2p orbitals overlapping form a pi orbital
What is the bond angle around the C=C?
120 ( planar)
Discuss the solubility in alkenes
Non-polar so they are insoluble in water but soluble in organic solvents
What is the main reaction of alkenes?
Electrophilic addition.
C-C and C-H are called…… bonds
C-C and C-H are called sigma bonds.
What colour flame does complete combustion give?
Blue
What products does complete combustion give?
ONLY carbon dioxide and water
What colour flame does incomplete combustion give?
Smoky orange
Incomplete combustion is much more likely with ……. chain alkanes. Why?
Longer chain alkanes as they need more oxygen to combust completely
What does incomplete combustion produce?
SOME water+carbon dioxide
Also: pure carbons, hydrocarbons and carbon monoxide.
How do you test for alkenes?
Bromine water is light orange and will be decolourised in the presence of an alkene
Name two types of compound that are produced by reforming
Cycloalkanes and aromatic hydrocarbons
What state do combustion reactions happen between?
Combustion reactions happen between GASES.
Explain how geometric isomerism arises
Restricted rotation around double bond
Poly(propene) doesn’t have a sharp melting temperature. Suggest why.
Different chain lengths.
What does inert mean?
having little or no ability to react (stable)
What happens when you burn poly(chloroethene)?
Toxic gases are released
Isomers have different……
Skeletal formula
List pollutants formed during the combustion of alkane fuels
carbon monoxide, oxides of nitrogen and sulfur (acid rain), carbon particulates and unburned hydrocarbons.
Describe what is meant by “reforming”
processing of straight chain hydrocarbons into branched-chain alkanes or cyclic hydrocarbons for efficient combustion
What type of bonds does a double bond consist of?
A sigma and a pi bond
How is a pi bond formed?
When two lobes of two p orbitals overlap adjacently (one above and one below the carbon atom)
How is a sigma bond formed?
When two orbitals overlap in a straight line in the space between two atoms.
The C=C is made up of two different types of bond.
Name a similarity between these bonds.
Both bonds form when atomic orbitals overlap.
The C=C is made up of two different types of bond.
Name 2 differences between these bonds.
Sigma bonds have a higher bond enthalpy than pi bonds.
In sigma bonds e- density lies directly between two nuclei but in pi bonds the electron density lies above and below the molecular axis.
When naming isomers, when will you use “cis” and “trans”?
When there are two identical groups either side of the bond.
What does cis mean?
Cis means the same groups are on the SAME SIDE of the double bond.
What does trans mean?
Trans means the same groups are on OPPOSITE SIDES of the double bond.
Adding …… to C=C bonds produces Alkanes. Requiring a ……. catalyst.
Adding hydrogen to C=C bonds produces Alkanes, in the presence of a NICKEL catalyst and 150”c
What is Markownikoffs rule?
The major product from addition of a hydrogen halide to an unsymmetrical alkene is the one where hydrogen adds to the carbon with the most hydrogens already attached
Name 3 ways to dispose of polymers
Buried, Reused, Burned.
What happens when you dehydrate an alcohol?
Forms an Alkene
How would you dehydrate an alcohol?
By eliminating water by adding an acid catalyst like concentrated PHOSPHORIC ACID (H2PO4). Then heat it.
The simplest way to oxidise alcohols is to…..
burn them
What does the extent of oxidation of an alcohol depend on?
Structure:
Primary- forms aldehydes and carboxylic acids
Secondary- Ketones only
Tertiary- NOT OXIDISED. (only if burnt)
What type of bond do aldehydes and ketones contain?
C=O bonds.
How would you mildly oxidise alcohols?
Adding an oxidising agent like acidified dichromate (VI)
How can you test is something is an aldehyde or a ketone?
Benedicts solution (Copper II ions dissolved in sodium carbonate) BLUE copper II ions reduced to a brick red precipitate of Copper (I) oxide if HEATED with aldehyde, if heated with ketone nothing happens.
Which do you distil or reflux to form out of aldehydes and carboxylic acids?
Distil for aldehyde.
Reflux for carboxylic acid.
ethanoic acid smells of…
vinegar
Primary Alcohols oxidise to …… and ……..
Aldehydes and carboxylic acids.
Secondary alcohols will oxidise to….
Ketones
The only way to oxidise tertiary alcohols is by…..
burning them.
Why is it important to use distillation for an aldehyde?
So the aldehyde is removed immediately as it forms.
What is a functional group?
Group of atoms responsible for characteristic reactions of a compound.
What reactions will alkanes undergo?
Combustion and reactions with halogens
What is incomplete combustion and what products are formed in the case of alkanes?
Combustion in a limited supply of oxygen.
CO + CO2 + H2O
What are biofuels?
Fuels developed from renewable resources.
Give an advantage and disadvantage of biofuels
Less food crops grown as space used for crops for biofuel.
Reduces use of non-renewable fossil fuels.
Limitations of free radical substitution?
If there is an excess halogen further substitution happens and its harder to separate desired product from others.
Which bond is responsible for the lack of rotation around a C=C?
A pi bond.
What requirements does the addition of H to an alkene have?
A nickel catalyst and 150 degrees.
Name 3 ways to dispose of polymers
Reusing them- some recycled by melting and remoulding, some cracked into monomers
Burning- Heat generates electricity
Buried- Landfill used if it’s difficult to separate from other waste or to technically recycle.
List 3 things that chemists have to do when making sustainable polymers
Energy use kept to minimum so catalysts used.
Use renewable raw materials wherever possible
Limit waste products made especially if hazardous to human health/environment.
Name 2 advantages and 1 disadvantage of biodegradable polymers.
Raw materials won’t run out like oil will
Plant based polymers save energy compared to oil based plastics.
BUT they’re more expensive than oil based equivalents.
How to test for presence of alkene?
Brown bromine water decolourises.
Define a fraction
mixture of compounds with similar boiling points therefore chain length.
What is acidified potassium manganate used for?
Added to alkene to form a diol
purple to colourless
What catalyst is used for Catalytic Cracking?
Zeolite catalyst.
What are the main products of catalytic cracking?
Aromatic hydrocarbons
When can you use cis/trans isomerism?
When the carbon atoms have at least one group in common
How is margarine made?
Hydrogenating vegetable oils by removing some double bonds the melting temp raises so that it becomes solid at room temp.
How do you produce an alcohol?
steam + alkene via phosphoric acid catalyst = alcohol
How is a diol produced?
Alkene with acidified potassium manganate -> diol
oxidises the double bond
(purple and decolourises )
3-methylbutan-2-one may be prepared by oxidising 3-methylbutan-2-ol. Why can 3-methylbutanoic acid NOT be formed from this?
As secondary alcohols cannot be oxidised to carboxylic acid.
