paper three stuff Flashcards
Define a homologous series
A family of compounds with similar chemical properties and structures that are differentiated by a CH2 group
What is the difference between a sigma and pi bond?
Sigma bond: The direct overlap of orbitals of each bonding atom
Pi bond: The sideways overlap of two adjacent p orbitals
What is required for E/Z isomerism and Cis/Trans isomerism?
E/Z: A double bond and each bonded carbon much be attached to each carbon atom of the double bond
Cis/Trans: One of the attached groups must be the same for both groups
Why is C-Cl have a higher bond enthalpy than C-I?
Because C-CL have a higher difference in electronegativity and a higher bond enthalpy than the bond in C-I
How do chlorine radicals catalyse the breakdown of the ozone layer?
Cl* + O3 -> CLO* + O2
CLO* + O -> O2 + Cl*
O3 + O -> 2O2
Chlorine catalyse the breakdown of the ozone layer and stay in the atmosphere for a long time due to the strong halogen-carbon bonds
How do you purify impure solids by recrystallisation?
1) Use minimum volume of HOT solvent to dissolve product
2) Use Bucher funnel and do reduced pressure filteration
3) Wash with a fresh cold solvent and leave on a dry paper towel to dry
What are methods of finding out a purity or identity of a substance?
Determining melting point and comparing to a known data base, the more pure the substance the sharper and well defined melting point it will have.
Also could use thin layer chromatography and compare to the known pure sample
Spectroscopy techniques
How do you obtain and purify an organic liquid?
Add alcohol and HCL into a separating funnel, place stopper, shake vigoursly and release pressure when required
Allow mixture to separate and collect bottom layer
Distill and collect impurities
Why should water in a condenser be used from the bottom to the top?
Maximise heat transfer for condensation and prevent the water filling in incorrectly
What is the equation for atom economy and how can you increase it?
Atom economy is : Mr of desired products/Mr of all products x 100
To increase atom economy, you can find uses for the waste products
What does an M+1 peak indicate?
An isotope with a higher MR than the original element
Why is phenol and alkenes more reactive than benzene?
Because Benzene has a delocalised system of Pi electrons with low electron density therefore is unable to polarise certain reactants such as halogens and haloalkanes.
Describe the delocalised model of benzene
Adjacent p-orbitals overlap above and below the plane
Consists of a system of delocalised pi electrons
Overall low electron density
What happens when a polyester goes through acid and alkaline hydrolysis?
Acid: Carboxylic acid and alcohol
Alkaline: Salt and Alcohol
What happens when a polyamide goes through acid and alkaline hydrolysis?
Acid: NH3+ and carboxylic acid
Alkaline: Salt and amine, NH2
How does TLC separate and identify compounds?
Based on the different affinities for the adsorbent during the stationary phase, the retention factor is calculated and compared against a pure sample or run against a pure sample
What does gas chromatography depend on?
Gas chromatography depends on the solubility of the components during the liquid stationary phase.
The more soluble the the slower it will move and therefore lower the retention time
What is the difference between structural isomers and steroisomers?
Structural isomers: The same molecular formulae but different structural formulae
Stereoisomers: Same structural formulae but different arrangements of atoms in a space
What happens when you react an acyl chloride and a NH2 group?
Forms an amide
How do you get from a haloalkane to NH2 group?
By adding ethanol and excess ammonia
How do you get from a nitrile to a carboxylic acid?
Through aqueous acid hydrolysis
How do you go from an alcohol to a haloalkane?
React with hydrogen halides that are formed in situ with an acid and a sodium halide.
For example H2SO4 and NaBr which will produce HBr that will react with the alcohol
How would you purify a liquid distillate?
+ Add a neutralising agent such as Na2CO3
+ Dry with an anhydrous salt, e.g MgSO4
+ Redistill at 44*
What are some limitations of organic synthesis involving radical substituion?
Substitution could occur at different points along the chain
Formation of unwanted products during termination
How do you get from a carboxylic acid to an acyl chloride and what other products are produced?
Carboxylic acid + Thionyl chloride (SoCl2) makes an Acyl chloride and SO2 and 2HCL
Why are mechanisms called heterolytic and homolytic FISSION
Involve the breaking of a covalent bond
Heterolytic: One of the bonding atom receives both of the bonding electrons
Homolytic: Each one of the bonding atoms receive an electron from bonding pair
Why does C-F hydrolyse slower than C-CL?
What set up would you require to test this?
Because C-F has a higher bond enthalpy, therefore a stronger bond so therefore will take a slower time to hydrolyse.
Reflux set up, condenser with water and reflux pear shaped flask thing
