module 4.1- core organic Flashcards
define organic chemistry
study of the structure, properties, composition, reactions and preparation of carbon-containing compounds
why is carbon so special?
in group 4, each carbon can form four covalent bonds to other atoms, can form long chains with triple or double bonds
define saturated (in terms of hydrocarbons)
contains only single bonds, fully saturated carbons
are alkenes saturated or unsaturated?
unsaturated as they contain a carbon-carbon double bond
define homologous series
a family of compounds with similar chemical properties whose SUCCESSIVE members differ by the addition of a -CH2- group
define functional group
the part of the organic molecule that is largely responsible for the molecule’s chemical properties.
what are the three classes of hydrocarbons
aliphatic - carbon atoms joined to each other in unbranched (straight) or branched chains, or non-aromatic rings
alicyclic - carbon atoms are joined to each other in a ring (cyclic) structure, with or without branches
aromatic - some or all of the carbons are found in a benzene ring
what does the stem, prefix and suffix indicate about hydrocarbons
stem - indicates the number of carbon atoms in the longest continuous chain of the molecule
prefix - indicates the presence of side chains or functional groups
suffix - indicates functional groups
what are the three homologous series of aliphatic hydrocarbons that you need to know
alkanes - single carbon-to-carbon bonds
alkenes - double carbon-to-carbon bonds
alkynes - triple carbon-to-carbon bonds
how do you name aliphatic alkanes
(4steps)
- all alkanes have the suffix -ane
- identify the longest continuous chain of carbon atoms and name it
- identify side chains attached to “parent chain”. the name of the alkyl group is added as a prefix to the name of the parent chain
- add numbers before any alkyl groups to show the position of the alkyl groups on the parent chain
how do you name alicyclic alkanes ?
same as aliphatic alkanes but add the prefix cyclo- to show carbon atoms are arranged in a ring structure
what is the functional group and suffix of an aldehyde
-CHO (oxygen double bonded to carbon)
suffix= -al
what is the functional group and suffix of a ketone
-C(CO)C- (co double bond)
suffix = -one
what is the functional group and suffix of an ester
-cooc- (first oxygen double bonded)
-oate = suffix
what is the functional group and suffix of an acyl chloride
-COCl (carbon and oxygen double bonded)
suffix = -oyl chloride
what is the functional group and prefix AND suffix of an amine
-NH2
prefix= amino-
suffix= -amine
what is the functional group and suffix of a nitrile
-CN (triple bond)
suffix = -nitrile
how do you write the skeletal formula
a line represents a single bond
an intersection of two lines represents a carbon atom
the end of a line represents a CH3 group
define nomenclature
the system used for naming organic compounds
what is the difference between molecular and empirical formula
empirical is the simplest whole number ratio of atoms whereas molecular is the actual number of atoms of different elements in a molecule
what does displayed formula mean
shows every atom and every bond in a molecule
give the suffixes for:
1. no double bonds
2. at least 1 double bond
3. an alcohol
4. an aldehyde
5. a ketone
6 a carboxylic acid
- -ane
- -ene
- -ol
- -al
- -one
- oic acid
define structural isomerism
when molecules have the same molecular formula but different structural formula
what are the 3 types of structural isomerism
chain - different chain length caused by branching
positional - position of the functional group changes
functional group - composition of the compound can change the functional group
what are the 3 functional group isomers of C3H8O
propan-1-ol
propan-2-ol
methoxethane - ether - 2 carbonds bonded directly to oxygen (COC) not (COH)
how can isomers change the physical properties of a compound
Different intermolecular forces between molecules can lead to differences in
boiling/melting points, viscosities, solubilities, densities etc.
how can isomers change the chemical properties of a compound
Different functional groups can have different interactions with biological systems
(toxicity), reactivity, bond enthalpy, flammability, oxidation states etc.
what makes alkanes saturated
only contains single sigma bonds
what is a sigma bond
a strong covalent bond formed by overlap of atomic orbitals along the bond axis (i.e. on the line connected by the 2 bonded atoms)
what does having a sigma bond mean for the atoms mobility
atoms can rotate freely around a sigma bond and molecule shapes are not rigid.
what is the shape of alkanes and why is it like this?
tetrahedral 109.4 degree bond angle
because each carbon is surrounded by 4 electron pairs in four sigma bonds. the repulsion of these electron pairs results in the 3D tetrahedral arrangement around each carbon atom
what is the order of priority in nomenclature for the function groups
highest - lowest
and their suffix/ prefix
carboxylic acid -oic acid
ester -oate
amide -amide
nitrile -nitrile
aldehyde -al
ketone -one
alcohol -ol or hydroxy-
amine -amine or amino-
alkene -ene
alkyne -yne
alkane -ane
ether alkoxy-
alkyl halide halo-
what are the two types of bond fission?
homolytic fission - each of the bonded atoms takes one of the electrons from the covalent bond
heterolytic fission - one of the atoms takes both electrons from the covalent bond resulting in a negative and positive ion
what do reaction mechanisms tell you?
HOW the reaction takes place
what do curly arrows in reaction mechanisms tell you
show the movement of the electron pairs when bonds are broken or made
what is a radical
an atom or group of atoms with an unpaired electron
how do curly arrows represent homolytic fission
as one electron goes to each atom, a “fish hook” arrow goes opposite ways using half an arrow head at each end to show two electrons moving
what are an atom or group of atoms with an unpaired electron called
a radical
what are the three types of reaction mechanisms
addition - two reactions form one product
substitution - an atom, or group of atoms, is replaced by a different atom or group of atoms
elimination - removal of a small molecule from a larger one. one reactant forms two products
what is the difference between a nitrile, an amine and an amide
nitrile is nitrogen triple bonded to carbon
amine = NH2
amide = oxygen double bonded to carbon, carbon bonded to NH2
in nomenclature, how do you order the haloalkane functional groups if there are more than one
eg. bromo, fluoro, iodo
alphabetically
bromo, chloro, fluoro, iodo
what two things affect the boiling points of alkanes and how?
- number of carbons in the chain - increases - more points of contact/ greater surface area, increases london dispersion forces
- branches - decrease - unable to pack tightly together so reducing points of contact.
which has a greater effect on the boiling point of alkanes - number of carbons or branches
number of carbons
why are alkanes non-polar
the difference in electronegativity between carbon and hydrogen is very small and alkanes have a symmetrical tetrahedral shape so no polar bonds
what colour are the flames of
a. complete
b. incomplete
combustion of alkanes
complete = blue flame
incomplete = orange flame
what are the limitations of radical substitution?
radicals are very reactive, therefore:
- multi-substitution can occur, lots of termination steps
- limited control over reaction - unwanted waste products form
- no control over what point on the C chain where the reaction occurs
- can produce longer alkanes - have to be separated
-waste products from side reactions
what is the colour of ethanoic acid in
1. litmus indicator
2. universal indicator
- light red
- orange
what is the colour of hydrochloric acid in
1. litmus indicator
2. universal
- dark red
- red
what observations from ethanoic acid with:
1. magnesium
2. sodium carbonate
- slight fizzing
- less CO2 produced - slow reaction
what observations from hydrochloric acid with:
1. magnesium
2. sodium carbonate
- rapid fizzing
- fast reaction - lots of CO2 gas produced
what bonds are present in alkanes
LDFs and Instantaneous dipole interactions
true or false “incomplete combustion is more likely with a shorter chain”
false - more likely with a longer chain
what bonds make up a C=C bond?
one sigma bond on the bond axis and one Pi bond above and below the carbons
what is the reactivity of alkanes like?
very low reactivity due to sigma bonds having:
low polarity
high bond enthalpy - energy required to break the bonds
what properties increase and decrease as size of alkanes increase
boiling point increases
volatility (how easily to turn to gas) decreases
viscosity (how easily it flows) - increases
flammability - decreases
how are balanced combustion equations of alkanes given?
the fuel is one mole and the oxygen is given as halves
explain why nitrogen is often produced in the combustion of alkanes in cars and engines
due to the high temperatures, the nitrogen reacts with the oxygen in the atmosphere, forming nitrogen oxides
explain why straight chain isomers have higher boiling points than their branched chain isomers
straight chains can pack together more tightly, therefore have more points of contact/ greater surface area. increasing the strength of the london dispersion forces, requiring more energy to break the bonds
what are the three stages of radical chain reactions
(explain them)
- initiation - creates the radical species
- propagation - radicals react with stable molecules to displace an atom and form new radicals (substitution)
- termination - two free radicals react to form a stable adduct.
write an equation for the initiation stage of the reaction of chlorine with C4H10
what form of fission is this?
what are the conditions necessary?
Cl-Cl –> 2Cl ‘ - represents 2 radicals (unpaired electrons)
homolytic fission - one electron goes to each atom
conditions - UV
write an equation to show the propagation stages of the reaction of C4H10 + Chlorine (2 equations)
C4H10 + Cl’ –> C4H9’ + HCl
C4H9’ + Cl2 –> C4H9Cl + Cl’ (where ‘ represents radicals - lone electrons)
what shape forms around the double bonded carbon atoms in alkenes and what is the bond angle of the surrounding atoms
trigonal planar - 120degrees
what determines the shape around the double bonded carbons in alkenes
there are 3 regions of electron density around each carbon atom
the regions repel each other as far as possible,
all atoms are in the same plane
describe how the double carbon bond is formed in alkenes
3 electrons from the carbon are bonded to other atoms via sigma bonds. leaving one electron, in a p-orbital, then a Pi bond is formed.
Pi bonds are formed by the sideways overlap of the 2 p-orbitals, one from each carbon atom in the double bond. The Pi electron density is concentrated above and below the sigma bond joining the nuclei of the carbon atoms.
what are the properties of alkenes
insoluble in water - non-polar
boiling points increase with chain length - more points of contact = increased london dispersion forces
lower b.p. than equivalent alkane - lower Mr so fewer electrons and fewer london dispersion forces. alkenes don’t pack together as tightly due to both 109.5 and 120 degree bond angles.
define stereoisomerism
when molecules have the same structural formula but a different arrangement of the atoms in space
when does a molecule have E/Z isomerism
if it has:
a c=c double bond
and different groups attached to each carbon in the double bond.
what is the difference between E and Z isomers
E isomers have the 2 hydrogens at diagonally opposite sides of the two carbons, same for the other groups.
Z isomers have the hydrogens on the same side of the carbon double bond - either lower side or upper side
what is the difference between E/Z isomerism and Cis-Trans isomerism
Cis-Trans have to have same properties as E/Z but one of the attached groups on each carbon atom must be the same on each side
what is the Cahn-Ingold-Prelog nomenclature
atoms attached to the carbon bond are given priority based on their atomic number.
if both higher priority are on the same side = Z isomer
if higher priority are diagonally opposite = E isomer
what are the three chemical tests for alkenes
combustion - more sooty yellow flame due to higher percentage mass of carbon
decolourises bromine water from orange (shows unsaturation, can also be an alkyne)
oxidation - decolourises potassium manganate (acidified)
what type of fission occurs in electrophilic addition?
heterolytic fission (both electrons go to one element, forming 2 ions
in electrophilic addition, what initiates heterolytic fission in the covalent bonded addition molecule?
the Pi bond creates a region of high electron density above and below the molecule, inducing a dipole in the covalent bond
what is the common misconception of the Pi bond?
that the Pi bond is the double bond
actually the Pi bond forms as well as the sigma bond, creating a double bond
why are alkenes more reactive than alkanes
the Pi bond has a lower bond enthalpy so requires less energy to break.
the position of the Pi bond (above and below carbons) makes it easier to “attack” the electron pair
what reactions do all alkenes undergo?
electrophilic addition reactions
define electrophile?
electron pair acceptor - often positive ions or have a delta positive charge (electron deficient)
what are the reaction conditions for hydrogenation of an alkene
what is the product
reagent - Hydrogen (H2)
conditions - 150 degrees C, Nickel catalyst
product - alkane
what are the conditions for the bromination of alkenes
what is the product
reagent - Br2
conditions - N/A, mix at room temp
product - dibromoalkanes
what are the conditions for the reactions of alkenes and hydrogen halides?
what is the product?
reagent - HBr
conditions = N/A, mix at room temp
product - bromoalkane
what are the conditions for the hydration of alkenes
what is the product?
reagent - water (steam)
conditions - 300degrees C, 6MPa (60atm), H3PO4/H2SO4 catalyst
product - alcohol
why are most addition polymers not biodegradable?
because they contain no polar bonds and are therefore unreactive
why are polyesters and polyamides biodegradable?
because they are reactive due to weak polar bonds in the polymer chain
define biodegradability
the ability of a substance to be broken down physically and/or chemically by microorganisms
in biodegradation, what are the products of acidic hydrolysis and basic hydrolysis
acidic - original monomers produced
basic - salt of the dicarboxylic acid monomer produced
define photodegradability
when substances are broken down chemically using wavelengths similar to light (UV is most effective)
what are the pros and cons of biodegrading?
pros: reduces build up of landfill, cheap - no human interference required, monomers can be reused for other applications
cons: takes a long time, doesn’t fully break down. if a substance is biodegradable, it will have to be replaced meaning more pollution in the production of a replacement
what are the pros and cons of feedstock
pros: works with unwashed and unsorted polymers, 30-40 commercial technologies available to assist the method, recovers raw materials and primary energy from waste
cons: industrial installations are rare - poor profitability, high investment cost, frequent cleaning and maintenance, cost of catalysts etc.
what are the pros and cons of landfill
pros: contained in a specific location =, biodegradable polymers will slowly degrade
cons: limited land available, slow degradation, leaching of toxic compounds, gas emissions released (methane)
what are the pros and cons of incineration
pros: energy released can be used as electricity, takes up less space than landfill, prevents build-up on land
cons: toxic gases and particulates released, increased in CO2 emissions, expensive, big factories require lots of polymer building materials, people complain due to “eye sore” - sight pollution
what are the pros and cons of recycling
pros: reuse and conservation of finite hydrocarbons, less toxic gas released, reduction of landfill (eyesore), can also save people money eg. DIY upcycling
cons: collection, sorting and remoulding requires energy, expensive and time consuming.
