AS organics Flashcards
homologous series
a series of organic compounds containing the same functional group with sucessive members differing by -CH2
functional groups
a group of atoms responsible for the characteristic reactions of a compound
alkyl group
-CH3
aliphatic
carbon joined to each other branched (straight), unbranched or non-aromatic rings
alicyclic
carbon joined in rings
(with or without branch)
aromatic
some/ all carbons found in a benzene ring
unstaurated
contain C=C or C≡C
structural isomers
same molecular formula but different displayed formulae
What is the naming system for compounds
Nomenclature
Steps to naming organic compounds
- find longest unbranched backbone
- Add suffix for main functional group
- Number the functional groups and/or alkyl side chains
prefix of alcohol
hydroxy-
suffix of aldehyde
-al
suffix of ketone
-one
stems (from 0-10)
- meth-
- eth-
- pro-
- but-
- pent-
- hex-
- hept-
- oct-
- non-
- dec-
Homolytic
Each bonding atoms recieves one electronforming 2 radical
Hetrolytic
One of the bonding atoms recieves both electrons To form a cation and an anion
Radical
a reactive species with an unpaired electron
(but not charged)
Electrophile
(+ve) electron-deficient species , accepts electrons to form covalent bonds
Nucleophile
(-ve)electron-rich species, provides pair of electron to form covalent bonds
General formula of alkanes
CnH2n+2
what is the type of bond in alkanes
sigma bonds
How are sigma bonds formed?
The overlap of the s-orbitals
Why are alkanes non-polared molecules?
- electronegativity diff. between C - H are neglegible
- bonds are relatively non-polared
Structure of alkanes and its bond angles (why?)
Tetrahedral (109.5)
Factors affecting boiling point and (why?)
- Chain length
(↑C = ↑ S.A. = ↑ London forces)
(↑electron = ↑strength of london forces)
2.Branching
↑ branching = ↓ surface contact = ↓ london forces
Why is Alkanes unreactive
- ↑ bond enthalpy of C-C + H-H
- ↓ polarity of sigma bond
What must be present for free-radical substituition
UV light
Three steps of free radical substitution
- initiation
2.propagation
3.termination
Describle initiation of free radical substitution
Halogen molecules broken down in Homolytic fission, under UV
Describle propagation of free radical substitution
- radical attacks alkanes
- C-H bonds Homolytic fission occurs
- alkyl radical formed attacks halogen molecules
- forming haloalkane + halogen radical
Describle termination of free radical substitution
Two radical reacts together to form a single unreactive molecule
3 limitation of free radical substitution
- impurities in the product
- further substitution (when excess halogen under UV)
- substitution on different carbon (cannot control where hetrolytic fission occurs)
Two bonds in alkenes
σ and π
one characteristic of π bond
Fixed above and below the planar, prevent rotation of the molecule
Bond angles of alkene
120 - trigonal planar
How does E/Z isomer work ?
E - piority group on EPPOSITE side of plane
Z- piority group on ZAME side of plane
What is the CIP priority rules ?
- calculate the total atomic no of group
- Group with greatest atomic no is the priority group
4 types of alkene reactions
- hydrogenaton
- Halogenation
- hydrohalogenation
- hydration
what does hydrogenation form
alkane
what type of reaction are the reactions of alkene?
electrophilic addition
Observation of halogenation (Bromine)
orange to colourless
What does hydration form ?
Alcohol
Inductive effect
↑ C-C bonds
carbocation ↓ +ve charged
↓ reactive
What does the Markownikoff’s rule apply to ?
Only for assymterical molecules only
State Markownikoof’s rule
Rules favours **major **product here:
Halogen (HX) / most electronegative halogen
bonds to
MOST SUBSTITUITED CARBON
Major product of the reaction (hydrogen halide)
halogen to
higher class carboncation
Major product of the reaction (interhalogen)
↑electronegative halogen to
↑ stable carboncation
Minor product of the reaction (interhalogen)
less electronegative to
more stable carbocation
Define polymers
A large chain formed from many thousands of repeat units of smaller molecules
Define monomers
A small molecule that conbines with many other monomers to form a polymers
Repeating units
the smallest group of atoms that connected after the other make up the polymer chain
3 polymers waste managements
- recycling
2.combustion
3.feedstock recycling
What is feedstock recycling ?
polymers are broken down by chemical and thermal processes to form gases and fuel
4 types of alternative plastic solution
- Bioplastic - made from cellulose, starch…
- Biodegradable - breaks down naturally
- Compostable - made from plants + degrade naturally
- Photodegradable - break down under visible radiation
How are photodegradable polymers made
- Contains bonds that are weakened by absorbing light-
- can be an additive mixed into polymers to promote degradation
General formulae of alcohol
CnH2n+1 OH
Intermolecular forces involved in alcohol
- Hydrogen bonding - when oxygen (δ-)from one molecules attracts a hydrogen (δ+) on another alcohol
- Temporary D-D forces - ↑ chain = ↑ B.P.
Solubility of alcohol
- Small alcohol dissolves in water
- ↑ chain length= ↓ soluble
(As ↓ polared = ↓ likely to dissolve in polared solvent)
4 types of reaction of alcohol
- Combustion
- Oxidation
- Dehydration
- Substitution
Alcohol reactions
What are the three types of oxidation reactions? + reagents?
primary in distill = aldehyde
primary in reflux = carboxylic acid
secondary in reflux = ketone
What is the colour change of oxidation reaction of alcohol
Orange to green
2 types of Haloalkane reaction
- nucleophilic substitution
- elimination
Reactivity of haloalkane
(3 points)
1.↓electronegative down the group
2. ↓Polared bonds
3.↓bond enthalpy
4. ↓energy required to overcome
[↓ chain = more electronegative overall]
2 ways of hydrolysis of haloalkane
- by aq. alkali
- by water (with prescence of ethanol)
[both forms alcohol and halide]
Purpose of alcohol for hydrolysis by water
To enable the haloalkane organic layer to mix with water solvent
(haloalkane=non-polared, water=polared)
so won’t mix
- How to test for halide ions formation
- Explain the reactivity of haloalkane?
(quickest = iodoalkane)
(second = bromoalkane)
(slowest = chloroalkane)
… to form p.p.
- Add silver nitrate
(first to form p.p. = most reactive) - Iodoalkane is the most reactive
* least electronegative
* weakest bond C-I
* requires the least energy to overcome
Describle the environmental concern of organohalogens
(2 points)
- produces halogen radicals under UV
- which catalyses the break down of Earth’s protective ozone layer
2 example of organohalogens
CCl3F, CCl2F2
Eq. of halogens radical from organohalogens (which starting molecule = CF2Cl2)
CF2Cl2 -> CF2Cl* + *Cl
5 main organic techniques
- distillation
- heating under reflux
- redistillation
- BP determination
- Drying
Purpose of distillation
To seperate liquids with different BP
4 steps of distillation
- heat in round bottom flask
- lowest B.P. evaporates first
- pass through the condenser
- fraction then collected in a seperate flask
Purpose of reflux
to enable reaction to fully complete
Steps to heating under reflux
- continuously heat content
- liebig condenser to ensure all vapour condense
- So no reactant can escape via evaporation
What is redistillation ?
subsequent distillation carried our to obtain purer product
Purpose of boiling point determination
To compare to databook value as a measure of purity
4 steps to boiling point determination
- tightly pack the substance into capillary tube
- place into machine
- record the MP and the range
- compare to databook value
Two examples of drying agents for drying
Any anhydrous salt
(e.g. MgSO4 , CaCl2)
4 factors to determine synthesis routes
- type of reaction - % yield
- Reagent used - renewable ?
- By-product , harmful/ toxic ?
- Catalyst - Rates , cost
How to test for 1* /2* alcohol ?
Add potassium dichromate result: orange -> green
How to test for aldehyde ?
Add tollen’s reagent Result : colourless -> dark silver p.p) MIRROR EFFECT
Test for haloalkane
Add silver nitrate and ethanol Result :
white p.p. = chloroalkane
creamy p.p = bromoalkane
yellow p.p = iodoalkane
What is Infrared spectrometry ?
- IR radiation causes covalent bonds to vibrate and abosrb energy
2.The spectrum of absorption can be used to determine functional groups
What + Where is the fingerprint region ?
to determine exact molecules
< 1500 cm-1
Environmental impact of IR radiation
- Atomospheric gas (e.g. CO2, H2O , CH4) aborbs IR radition
- exacerbates global warming
- emission usually from fossil fuel usage
Application of IR radiation
- monitor gases that cause air pollution
- modern breathalysers to measure ethanol
Define Time of Flight in mass spec
time for each ion to reach detector
Steps of mass spec
- Sample is vapourised and pass through high voltage
- Accelerated by -ve charged plates
- deflected by magnetic field
- reach detector to form spectrum
3 main peaks to focus on mass spec
- Molecular peak - second rightmost peak (tells molecualr mass )
- M+1 peak - right most peak (mass of compound with Carbon -13 isotopes)
- framgent peaks - any peaks < RFM (fragment ions of the molecule detected)
Markownikoff’s rule
What does it means by most-substituted carbon
carbon where it has the most no. of H replaced by C.
i.e. highest class carbon
Markownikoff’s rule
Why does higher class carbocation more stable?
- carbon bonded to more C
- non-polared bonds = more stable
- ↓ +ve carbocation
- ↑ stable (as ↓ likely to react)
Markownikoff’s rule
Why does the more stable carbocation forms major product?
- more likely form
- as ↓ likely to be attacked
- less energy needed to form
2 eq for the breakdown of ozone
3 condition of hydrogenation
- 200 °C
- 1000 KPa
- Nickel catalyst
2 condition for hydration
- 300 °C - reflux
- sulfuric / phosphoric acid
What bonds do C in C=C make
2 σ with hydrogen
1 σ in C=C
1 π in C=C
Where are σ bonds found
- C-H bond (1)
- C-C bond (1)
- C=C bond (1)
Optical isomerism
Non-superimposed mirror image
What is the difference between esterification and acid hydrolysis
Esterification - conc
Acid hydrolysis - diluted
