Organic Chemistry Flashcards
what does nomenclature mean?
The system used for naming organic compounds
What does the term empirical formula mean?
Simplest whole number ratio of atoms in a molecule
What does the term displayed formula mean?
It shows every atom and every bond in a molecule
What does the term structural formula mean?
It shows the arrangement of atoms in a molecule without showing every bond
Define skeletal formula
A type of formula which is drawn as lines with each vertex being a carbon atom. Carbon atoms not drawn, assumed each C atom has all unspecified bonds as C-H
Define homologous series
A series of organic compounds having the same functional group but with each successive member differing by CH2
What is a functional group?
A group of atoms responsible for characteristic reactions of a compound
Give the suffixes for:
- No double bonds
- At least one double bond
- An alcohol
- An Aldehyde
- A ketone
- A carboxylic acid
- No double bonds (-ane)
- At least one double bond (- ene)
- An alcohol (-ol)
- An aldehyde (-al)
- A ketone (-one)
- A carboxylic acid (-oic acid)
Give the prefixes for:
- CH3 group
- C2H5 group
- C3H7 group
- C4H9 group
- Cl group
- Br group
- I group
- CH3 group ( Methyl -)
- C2H5 group (ethyl -)
- C3H7 group ( Propyl-)
- C4H9 group (butyl-)
- Cl group (chloro-)
- Br group (bromo-)
- I group (iodo-)
What is the general formula of alkanes?
CnH2n+2
What is the general formula for alkenes?
CnH2n
What does saturated mean?
Organic compounds which only contain single bonds
What are unsaturated compounds?
Organic compounds that contain at least one carbon-carbon double covalent bond
Define structural isomerism
When molecules have the same molecular formula but different structural formula
What are the 3 ways in which structural isomers can be formed?
- Alkyl groups can be in different places
- Functional groups can be bonded to different parts
- There can be different functional groups
What are stereoisomers?
Organic compounds with the same molecular formula but have different arrangement of atoms in space
What is E-Z isomerism and how are the E and Z isomers decided?
E-Z isomerism is caused by the limited rotation about carbon to carbon double bonds
If the two substituents with the highest molecular mass are on the same side of t he double bond, it is the Z (Zusammen) isomer
if they are on different sides, it is the E ( Entgegen) isomer
What is Cis-tans isomerism?
Special type of E/Z isomerism where the two substituents on each carbon atom are the same
What is homolytic fission?
it happens when each bonding atom receives one electron from the bonded pair forming two radicals
What is heterolytic fission?
When one bonding atom receives both electrons from the bonded pair
What are radicals?
Highly reactive, neutral species
How is a covalent bond formed from two radicals?
The radicals collide and the electrons are involved in the bond formation
What is an alkane?
A saturated hydrocarbon containing C-H bonds only
How are alkane fuels obtained?
Alkane fuels are obtained from the fractional distillation, cracking and reforming crude oil`
Describe the process of fractional distillation
- The oil is pre-heated then passed into a column
- The fractions condense at different heights and the temperature of column decreases upwards
- The separation of the fuels depends on boiling point which depends on size of molecules. The larger the molecule the larger the London forces
- Similar molecules( size, bp, mass) condense together and so are collected at the same fraction
- Small molecules condense at the top at lower temperatures and big molecules condense at the bottom at higher temperatures
What is cracking?
It is the process of converting large hydrocarbons to smaller molecules by breakage of C-C bonds
What is the reforming of crude oil?
It is the processing of straight-chain hydrocarbons into branched-chain alkanes and cyclic hydrocarbons for efficient combustion
What is the shape and angle of alkane?
Tetrahedral
109.5 degrees
Describe the (sigma) bond in alkane
The sigma bond is a covalent bond which has a direct overlap of the electron clouds of the bonding atoms
How reactive are alkanes?
Very unreactive
What reactions will alkanes undergo?
Combustion and reaction with halogens
What type of reaction is combustion?
Oxidation reaction
What is complete combustion?
combustion that occurs with plentiful supply of air
Write an equation for the complete combustion of octane
C8H18 (g) + 12.5 O2 (g) -> 8CO2 (g) + 9H2O (l)
What are the products of complete combustion when alkanes are used?
Carbon dioxide and water
What is the color of the Bunsen burner flame during complete combustion?
Blue flame
What is incomplete combustion and what products are formed in the case of alkanes?
- combustion in a limited supply of oxygen
- products: Water, carbon dioxide and carbon dioxide
Write an equation for the complete combustion of propane
C3H8 + 5 O2 –> 3 CO2 + 4H2O
What type of hydrocarbon are most likely to undergo incomplete combustion?
Longer chains
What are the pollutants formed in the combustion of alkanes?
Carbon monoxide, oxides of nitrogen and sulfur, carbon particulates and unburned hydrocarbons
What is the environmental impact of carbon monoxide?
It is toxic/ poisonous
What is the environmental impact of soot (carbon)?
Asthma, cancer, global dimming
What are the environmental impacts of nitrogen oxides?
NO is toxic and can form smog
NO2 is toxic and acidic and forms acid rain
What are the environmental impacts of unbranched hydrocarbons?
They contribute towards formation of smog
What is the importance of a catalytic converter?
These remove CO, nitrogen and unburned hydrocarbons
(e.g Octane, C8H18) from the exhaust gases turning them into less toxic products CO2, N2 and H2O
What are biofuels?
They are fuels developed from renewable resources. Alcohols and biodiesel are examples of renewable plant-based fuels
What are the advantages and disadvantages of biofuels?
Advantages
- Reduces use of non-renewable fossil fuels
- Use of biodiesel is more carbon-neutral
- Fossil fuels can be used as feedstock for organic compounds
- Less large scale pollution
Disadvantages
- Less food crops may be grown because crops for biofuels would be grown instead
- Reduction of rain forest that have to be cut down to provide land
- Shortage of fertile soils
How are halogenoalkanes formed from alkanes?
radical substitution
In the presence of what does alkane react with halogens?
UV light
What are the three stages of free radical substitution?
- initiation - breaking halogen bond to form free radicals
- Propagation - Chain part of reaction where prods are formed but free radical remains
- Termination - Free radicals removed, stable products formed
Write equations for the reaction of CH4 with Cl2 to form CH3Cl
Initiation: Cl2 –> 2Cl. (In presence of UV light)
Propagation: Cl. + CH4 –> HCl + . CH3 then
. CH3 + Cl2 –> CH3Cl + Cl.
Termination:
.CH3 + Cl. –> CH3Cl
2Cl. –> Cl2
. CH3 + .CH3 –>CH3CH3
What are the limitations of free radical substitution?
If there is excess halogen further substitution will take place therefore the desired product will be harder to separate from the others
What are alkenes?
unsaturated hydrocarbons that contain at least one Carbon to carbon double bond may up of a pi bond and a sigma bond
How is a pi bond formed?
Electrons in the adjacent p orbitals overlap above and below the carbon atoms. They can only be made after a sigma bond is formed
What bond restricts the rotation of carbon atoms?
Pi bond
What is the angle and shape of a double bond?
Trigonal planar
120 degrees
What is the qualitative test for alkanes?
This tests for Carbon to carbon double bond using bromine water. If the alkane is present bromine water decolorizes
Are they more or less reactive than alkanes? Why?
More reactive due to high electron density of double bond and the fact that the pi-bond is slightly easier to break
What intermolecular forces of attraction do they have?
only London forces due to non-polar bonds
Write an equation for the complete combustion of pent-3-ene
CH3CHCHCH2CH3 + 7.5 O2 –> 5O2 + 5H2O
What are the types of isomers that can be formed using alkenes?
E/Z isomers - due to the restricted rotation
Cis-tans isomers - if two of the same substituents are attached to each carbon
What is an electrophile?
Species that are electron pair acceptors
What is the most stable type of carbocation intermediate? Why?
Alkyl groups have a positive inductive effect, so the most stable carbocation is the one bonded to the most other carbon atoms i.e. A tertiary carbocation
Major products will be formed from which kinds of carbocations?
Tertiary (or the most stable available)
What conditions are needed for the electrophilic addition of H2O to an alkene? What is this type of reaction called?
- Stem in the presence of an acid catalyst, usually phosphoric acid
- Reaction is called hydration
What are the products of the hydration reaction?
An alcohol
What conditions are needed for the electrophilic addition of a hydrogen halide to an alkene?
hydrogen halide gases must be at room temperature
What is the reaction called when a halogen is added to alkene?
Halogenation
How does a molecule with a non-polar bond react as if it an electrophile?
Carbon to carbon double bond with a high electron density induces a temporary dipole in the halogen molecule –> positive dipole atom attracted to double bond
How can an alkene be converted into an alkane/ What is the reaction called and what are the required conditions?
-Alkene + Hydrogen = Alkane
- Hydrogenation
- Conditions –> 150 degrees celsius, nickel catalyst
What is an addition polymer?
Many monomers bonded together via rearrangement of bonds without the loss of any atom molecule
What are monomers? What form do they usually take?
- Molecules which combine to form a polymer
- Usually have a carbon to carbon double bond which breaks to leave a repeating pattern
What are the ways in which plastics can be disposed? (6)
- Landfill
- Combustion
- Electricity generation
- Reuse
- Recycle
- Organic feedstock
what are the disadvantages of recycling?
- plastics must be sorted into different types
- Expensive
- Labor intensive
- Requires high technology
How can chemists limit the problems caused by polymer disposal?
- Developing biodegradable polymers
- Removing toxic waster gases caused by incineration of plastics
Explain what happens in organic feedstock
Plastics are separated and broken down into small organic molecules through a series of reaction. The molecules can then be used to produce plastics and in other industries
What are halogenoalkanes?
Saturated organic compounds that contain carbon atoms and at least one halogen atom
Are halogenoalkanes soluble in water?
Insoluble as C-H bonds are non-polar, not compensated for enough by C-X bond polarity
Do halogenoalkanes have a polar bond? Why?
Yes polar, as halogen has a higher electronegativity than C ( halogen has a negative dipole, carbon has a positive dipole)
What type of intermolecular forces do halogenoalkanes have? Why?
-Permanent dipole-dipole and London forces of attraction
- C-X bond polarity creates permanent dipoles
When would they have higher boiling points?
- increase carbon chain length
- Halogen further down group 7
How would the mass of a halogenoalkane compare with the mass of an alkane of the same chain length?
Greater as mass of halogen is greater than mass of H
What is the most important factor in determining halogen reactivity?
The strength of carbon halogen bond
What would bond polarity suggest the order of reactivity would be?
C-F would be most reactive as most polar bonds
What would bond enthalpies suggest the order of reactivity would be?
C-l would be most reactive as lowest bond enthalpy
what is the trend in reactivity of primary, secondary and tertiary halogenoalkanes?
- The tertiary halide produces a precipitate almost instantly.
- The secondary halide gives a slight precipitate after a few seconds
- The primary halide takes considerably longer to produce a precipitate
Define a nucleophile
Electron pair donor
Give three examples of nucleophiles
: OH-
: CN-
: NH3
what is nucleophilic substitution?
A reaction where a nucleophile donates a lone pair of electrons to a positive dipole carbon atom, negative dipole atom leaves molecule (replaced by nucleophiles)
What is hydrolysis?
A reaction where water is a reactant
what reactant often produces hydroxide ions for hydrolysis?
water
What fission does water undergo to produce OH-?
Heterolytic fission
what are the conditions/ reactants needed for the elimination reaction of haloalkanes?
- NaOH or KOH dissolved in ethanol (no water present)
- Heated
What is formed in the elimination reaction of haloalkanes?
An alkane, water and hydrogen ion
How can you convert a haloalkane into an amine?
- Reagent: NH3 dissolved in ethanol
- Conditions: Heating under pressure in a sealed tube
- Mechanism: nucleophilic substitution
- Type of reagent: nucleophile- ammonia
How do you convert halogenoalkane into alkene?
use of ethanoic potassium hydroxide to produce alkenes ( Where the hydroxide ion acts as a base)
How do you produce nitriles from haloalkanes?
Use potassium cyanide to produce nitriles ( where the cyanide ion acts as a nucleophile)
How can you compare the rate of hydrolysis of haloalkanes?
Acqueous silver nitrate is added to a halogenoalkane and a silver halide precipitation is formed. The quicker the precipitate is formed the faster the rate of hydrolysis.
- AgI(s) - yellow precipitate
- AgBr(s) - cream precipitate
- AgCl (s) - White precipitate
forms faster in order of 3,2,1
What is the functional group of alcohol?
hydroxyl group - OH
What is the general formula of an alcohol?
CnH2n+1 OH
How do you name alcohols (one prefix, one suffix)?
Hydroxyl -OR -ol
What kind of intermolecular forces do alcohol have? Why?
Hydrogen bonding, due to the electronegativity difference in the OH bond
How do alcohols’ melting point and boiling point compare to other hydrocarbons’ of similar C chain lengths? Why?
Higher because they have hydrogen bonding (strongest type of intermolecular force) –> stronger than London forces
Are alcohols soluble in water? Why does solubility depend on chain length?
- Soluble when short chain- OH hydrogen bonds to hydrogen bond in water
-Insoluble when long chain- non polarity of C-H bond takes precedence
What makes an alcohol primary?
C bonded to OH is only bonded to one other C atom
What makes an alcohol secondary?
C bonded to OH is bonded to two other C atoms
What makes an alcohol tertiary?
C bonded to OH is bonded to three other C atoms
Write an equation for the combustion of ethanol
C2H5OH (l) + 3O2 (g) –> 2CO2 (g) + 3H2O (l)
What forms if you partially oxidize a primary alcohol?
An aldehyde
What conditions are needed to partially oxidize a primary alcohol?
- Dilute sulfuric acid
- potassium dichromate (VI)
- Distill product as it’s produced
- Gentle heating
Write an equation for the partial oxidation of ethanol
CH3 CH2 OH (l) + [O] –> CH3CHO (g) + H2O (l)
What forms if you fully oxidize a primary alcohol?
A carboxylic acid
What conditions are needed to fully oxidize a primary alcohol?
- Concentrated sulfuric acid
- potassium dichromate (VI)
- Reflux
- Strong heating
Write an equation for the full oxidation of ethanol
CH3 CH2 OH (l) + 2[O] -> CH2COOH (g) + H2O (l)
What forms if you oxidize a secondary alcohol?
A ketone
What conditions are needed for the oxidation of a secondary alcohol?
- Concentrated sulfuric acid
- Potassium dichromate (VI)
- Strong heating
Write an equation for the oxidation of propan-2-ol
is it possible to oxidize tertiary alcohol?
No
What is a dehydration reaction?
A reaction where water is lost to form an organic compound
What are the products of dehydration reaction of alcohol and the conditions needed?
- Alkene and water
- Concentrated sulfuric acid or concentrated phosphoric acid and 170 degrees celsius
How can you produce chloroalkanes from alcohols?
- Use PCl5 ( PCl 3/ conc HCl / SOCl2 / mixture of NaCl+ H2SO4 can also be used for substituting a Cl)
- E.g. CH2CH2 OH + PCl5 –> CH3 CH2 Cl + POCl3 + HCl
How can you produce bromoalkanes from alcohols?
Use 50% concentrated sulfuric acid and potassium bromide
How can you produce iodoalkanes from alcohols?
- Use red phosphorus and iodine
- Pl3 + 3CH3CH2 OH –> 3CH2 CH2 l + H2PO3
How do you prepare and purify a liquid organic compound?
- Heat under reflux
- Extract with a solvent in a separating funnel
- Distill
- Dry with an anhydrous salt
- Determine boiling temperature
