4.1 Flashcards
What do curly arrows represent ?
Flow of electron pairs during reaction mechanisms
What is a homologous series ?
Family of organic compounds that have same functional group but differ by CH2.
What is the bond angle of alkanes?
109.5
How does branching affect boiling point of alkanes ?
More branched=lower BP
Why does branching affect boiling point of alkanes?
More branches=molecules don’t fit together as neatly =fewer DD interactions
What are the 3 stages of radical substitution ?
1) initiation
2) propagation
3) termination
What is a pi bond formed by?
The electrons in adjacent p orbitals overlapping above+below atoms
what are aliphatic hydrocarbons?
where the carbon atoms are joined together in either straight or branched chains - NO BENZENE RING
what are alicyclic hydrocarbons?
where the carbon atoms are joined together in a ring structure but NO BENZENE RING
what are aromatic hydrocarbons?
where there’s at least 1 benzene ring in the structure
what are saturated compounds?
they contain only single covalent bonds between the carbons
what are unsaturated compounds?
contain at least one double carbon carbon bond.
what are structural isomers?
compounds with the same molecular formula but different structural formulae.
what are stereoisomers?
organic compounds which have the same structural formula but are arranged differently in space
what is homolytic fission?
when a covalent bond breaks and each electron goes to a different bonded atom, forming 2 radicals.
what is needed for homolytic fission to take place?
UV
what is heterolytic fission?
when a covalent bond breaks and both electrons go to one of the bonded atoms, forming oppositely charged ions.
what is the most stable carbocation?
TerTiary-when the carbon in the double bond is bonded to Three other carbons
what is the least stable carbocation?
PRIMARY=UNSTABLE- when the carbon in the double bond is bonded to 1 other carbon and 2 hydrogens
why are stereoisomers formed?
the RESTRICTED ROTATION of DOUBLE CARBON bonds
what has to happen for stereoisomers to exist?
- double carbon
- each carbon in double bond has to have 2 different groups attached to it.
what is a molecular formula?
the number of atoms in one molecule of the element/compound - each element only appears once.
what is a sigma bond?
an overlap of orbitals between 2 atoms-all single bonds, free to rotate
what is an example of orbital hybridisation?
2s1 2p3 becoming 4 lots of sp3
what is orbital hybridisation?
the concept of mixing atomic orbitals into new hybrid orbitals (with different energies, shapes, etc., than the component atomic orbitals) suitable for the pairing of electrons
what does the graph between boiling point of alkanes and no of Cs in alkanes look like?
increases but increases less each time-levels off
why does the graph between BP of alkanes and no of Cs look like how it looks?
the percentage of electrons you’re increasing the alkane by is shrinking each time, so there’s a smaller change in the induced dipole dipole forces.
what is the trend in boiling points of alkanes?
- increases with more Cs in formula
- straight chains have higher BPs than branched.
why do straight chains have a higher boiling point?
they can get closer together, increasing surface contact between molecules (NOT SA) giving more induced dipole forces
IF U DONT REVISE
u WILLflop
why do alkanes have a low reactivity with many reagents?
1) they have high bind enthalpy
2) the sigma bonds have a very low polarity
what are the 3 steps of homolytic substitution?
1) initiation
2) propagation
3) termination
what are the problems of free radical substitution?
- could go into wrong place on molecule-eg if you wanted 1-bromobutane but got 2-bromobutane
- different product =s formed at termination step
- multiple substitutions
what is the overall equation for the breakdown of ozone?
03+0»» 202
what are the propagation steps for the breakdown of ozone?
- Cl + 03»» •ClO + 02
* ClO + 0»» •Cl + 02
what is the general test for alkenes?
add bromine water- if it decolourises, it’s an alkene
what is the general formula for the hydrogenation of alkenes?
alkene + hydrogen»> alkane
what is hydrogenation of alkenes used for?
margarine manufacture
what is the catalyst needed for hydrogenation of alkenes?
nickel
what is the general equation for the hydration of alkenes?
alkene+water»» alcohol
what is the catalyst for hydration of alkenes?
phosphoric acid
what is the use of hydration of alkenes?
ethanol manufacture
what is a structural isomer?
Compounds with the same molecular formula but different structural formula.
what is homolytic fission?
breaking a covalent bond to form 2 radicals.
what is heterolytic fission?
Breaking a covalent bond to form two oppositely charged ions.
what is cis-trans isomerism?
A special case of E/Z isomerism in which two of the substituent groups attached to each carbon atom of the C=C group are the same.
what is an electrophile?
An electron pair acceptor
what is a structural isomer? (basic)
compounds with the same molecular formula but a different structural arrangement.
name 4 ways to process waste polymers.
1) recycling
2) landfill
3) combustion
4) organic feedstock/cracked/production of plastics/new polymers
what are 4 examples of a type of polymer being developed to minimise environmental damage?
- biodegradable
- compostable
- soluble
- photodegradable
give 3 reasons why there are many organic products formed in radical substitution
- multiple substitutions
- different radicals joining together at termination step
- termination steps can give products that will also react with bromine radicals.
what is a functional group?
group of atoms that is responsible for for the reactions/that gives the chemical properties
what is a radical?
something that has an unpaired electron.
explain why some molecules show stereoisomerism
the carbon-carbon double bond is non rotating (1)
each carbon of the double bond is attached to 2 different groups.
what are the problems of burning chlorine containing polymers?
produce toxic gases
produces HCl/acidic gas
produces dioxins
produces phosgene (?) (COCl2) (apparently it has respiratory effects)
what are 3 ways polymers can be processed to reduce their environmental impact?
combustion TO PRODUCE ENERGY
sorting and recycling
cracked ( to give monomers)/chemical feedstock
if they ask for a particular problem of burning a chlorine containing polymer, say…
it forms HCl
or
it forms chlorine
where is the sigma bond’s electron density?
between bonding electrons
where is the pi bond’s electron density?
above and below bonding atoms
how do you get rid of HCl from the toxic gases formed when burning a chlorine hydrocarbon?
add sodium hydrogencarbonate which NEUTRALISES IT
what is an alicyclic compound?
one that is both aliphatic and cyclic.
how do you know when something’s an E isomer?
priority groups on opposite sides of each c.
why do longer hydrocarbons have a higher melting point?
they have more SURFACE CONTACT so more induced dipole interactions.
how do u word when something’s formed bc of the carbocation rule?
the carbocation intermediate is more stable.
