Unit eight JCL Flashcards
how is a sigma bond formed
directly between two carbon atoms by the direct overlap of p orbitals
how is a pi bond formed
a pi bond is formed above and below the plane of carbon atoms by the sideways overlap of p orbitals
why is a pi bond easier to break than a sigma bond
a pi bond is more likely to break as it has a lower bond enthalpy compared to sigma bonds
why are alkenes insoluble in water
alkenes are non-polar and water is polar
why do alkene boiling points increase with chain length
chain length increases –> more points of contact –> more induced dipole-dipole interactions
define the term unsaturated
having carbon–carbon double or triple bonds and therefore not containing the greatest possible number of hydrogen atoms
what are the strongest intermolecular forces experienced by alkenes
induced dipole-dipole interactions
general formula for an alkene
CnC2n
what shape and bond angle do alkenes have around the C=C bond
120
trigonal planar
if an alkene has only one C=C bond, what shape and bond angle do the other carbons have along the chain
109.5
tetrahedral
isomerism definition
isomerism is where two or more compounds have the same molecular formula but a different arrangement of atoms
what are the two types of isomerism
stereoisomerism and structural
what is stereoisomerism
stereoisomerism occurs in compounds with the same structural formula but a different arrangement in space.
the pi bond in alkenes restricts the rotation of the molecule potentially causing E/Z isomerism to occur
what is required for E/Z isomerism to occur
a c=c double bond
each carbon is bonded to two different atoms/groups
why do alkanes not show stereoisomerism?
they don’t have pi bonds to restrict rotation
if a stereoisomer has two identical groups on the same plane of the molecule is it an E or Z isomer
Z isomer
if a stereoisomer has two identical groups on the opposite plane of the molecule is it an E or Z isomer
E isomer
what are Cis-Trans isomers
Cis-Trans isomers are a type of E/Z isomer where two of the substituent groups on the c=c bond are the same
what is an addition reaction
tow reactants combine to form one product
name the compound formed when ethene reacts with hydrogen
ethane
name the compound formed when ethene reacts with hydrogen chloride
chloroethane
name the compound formed when ethene reacts with water
ethanol
name the compound formed when ethene reacts with bromine
1,2-dibromoethane
what are conditions for hydrogenation
Nickle catalyst , 150C
what are the conditions for bromination
room temperature and pressure
what are the conditions for Hydration
H3PO4, 300C, 6MPa
what is an electrophile
an electron pair donor
what does a curly arrow represent
the movement of a pair of electrons
what does markovnikov’s rule state
the hydrogen being added bonds to the carbon with the most hydrogens present in the major product
what stabilises a carbonium ion
the induction effect of adjacent alkyl groups
the ability of alkyl groups to donate electrons
what is a monomer
a small molecule that can join together with other monomers to form a polymer
what is a polymer
a long molecule formed from lots of repeating units (monomers)
what is an addition polymer
a type of polymer formed from lots of alkenes joining together
what is a repeat unit
the part of a polymer that repeats (similar to a monomer but the double bond has been broken)
are alcohols polar or non-polar
polar
equation for the combustion of alcohols
Alcohol + oxygen –> Carbon Dioxide + water
what do you get when you reflux a primary alcohol with the oxidising agent of acidic potassium dichromate
Carboxylic acid
what do you get when you distill a primary alcohol with the oxidising agent of acidic potassium dichromate
Aldehyde
what do you get when you reflux a secondary alcohol with the oxidising agent of acidic potassium dichromate
Ketone
what does dehydration mean
removal of water
what is the colour change for the oxidising agent acidic potassium dichromate
orange –> green
what is a haloalkane
a compound in which a halogen has replaced at least one of the hydrogen atoms in an alkane chain
what is the general formula for a haloalkane
CnH2n+1X
define nucleophilic substitution
a type of substitution reaction in which a nucleophile is attracted to an electron-deficient centre or atom, where it donates a pair of electrons to form a covalent bond
which is more important, bond enthalpy or polarity
bond enthalpy
what is the formula of ozone
O3 molecules
what does CFC stand for
Chlorofluorocarbons
what happens when a CFC comes into contact with UV (equation)
CCl2F2 –uv–> •CClF2 + Cl•
how do CFCs break down the ozone layer (equation)
Cl• + O3 –> ClO• + O3
ClO• + O3 –> Cl• + 2O2
are CFCs inert?
yes
