4.1 Basics Concepts And Hydrocarbons Flashcards
What are the stem names for the first ten alkanes based on number of carbons?
1 carbon= meth-
2 carbons= eth-
3 carbons= prop-
4 carbons=but-
5 carbons=pent-
6 carbons=hex-
7 carbons=hept-
8 carbons=oct-
9 carbons=non-
10 carbons=dec-
What is nomenclature?
The system for naming compounds
Define a homologous series
A series of organic compounds having the same functional group but with each successive member differing by CH2
What are the names of the alkyl groups depending on their number of carbons?
1carbon= methyl-
2carbons=ethyl-
3carbons=propyl-
4carbons=butyl-
5carbons=pentyl-
6carbons=hexyl-
7carbons=heptyl-
8carbons=octyl-
9carbons=nonyl-
10carbons=decyl-
What is the general formula for an alkyl group?
CnH2n+1
-n=number of carbons
What is the general formula for alkanes?
CnH2n+2
-n=number of carbons
What is the general formula for alkenes?
CnH2n
-n=number of carbons
What is the general formula for an alcohol?
CnH2n+1 OH
-n=number of carbons
What is an aliphatic compound?
-a compound containing carbon and hydrogen joined together in straight chains,branched chains or non-aromatic rings
What is an alicyclic compound?
-an aliphatic compound arranged in non-aromatic rings with or without side chains
What is an aromatic compound?
A compound containing a benzene ring
What is a structural isomer?
Compounds with the same molecular formula but different structural formulae
What are the 3 ways structural isomers can happen?
-the alkyl groups are in different places
-the functional group can be bonded to different parts of the parent chain
-the functional group could be different
Define stereoisomers
-organic compounds with the same molecular formula and structural formula but having different arrangements of atoms in space
What is homolytic fission?
-each bonding atom receives one electron from the bonded pair, this forms 2 radicals
-and the breaking of a covalent bond
What is heterolytic fission?
-one bonding atom receives both electrons from the bonded pair and the covalent bond is broken
-this results in a cation and anion being formed
What is a radical?
A species with an unpaired electron
What are alkanes?
They are saturated hydrocarbons that contain single C-C and C-H bonds as sigma bonds (single)
They are free to rotate
What is a sigma bond?
An overlap of orbitals directly between the bonding atoms
What shape and bond angles do alkanes have?
-they have a tetrahedral shape with a bond angle of 109.5
What intermolecular bonding do alkanes have?
-carbon and hydrogen have very similar electro negativity values so alkane molecules are non-polar
-however as electrons are constantly moving at times there may be a lack of balance in charge distribution, causing an instantaneous dipole which will induce dipoles in neighbouring molecules
-this is called an induced dipole-dipole interaction or London force
What happens to the boiling points of alkanes as the carbon-chain length gets longer?
-as an alkane chain gets longer its molecular mass increases
-larger molecules also have more surface area contacts between adjacent molecules
-this increases the number of induced dipole-dipole interactions (London forces)
-so more energy is needed to overcome the intermolecular attraction so that the alkane can change state ,so the boiling point becomes higher the longer the carbon-chain length is
What effect does branching have on the boiling point of alkanes?
-the more branched a compound is the fewer surface interactions there are between molecules
-therefore branched molecules have fewer induced dipole-dipole interactions compared to a straight-chain isomer with the same molecular formula
-so branched molecules will have a lower boiling point than the equivalent straight chain isomer
Why do alkanes have a low reactivity with many reagents ?
-all the covalent bonds in alkane molecules have high bond enthalpies- so a large amount of energy is required to break the bonds
-the carbon-hydrogen sigma bonds have a very low polarity as the electronegativities of carbon and hydrogen are almost the same
What is complete combustion?
-there is a plentiful supply of oxygen and both carbon and hydrogen are oxidised
-it transfers the maximum amount of thermal energy
What is the equation for the complete combustion of methane ?
CH4 + 2O2———> CO2 + 2H2O
What is incomplete combustion?
-when an alkane is burnt in a limited supply of oxygen
-it produces carbon particles (soot) , water , carbon dioxide and carbon monoxide (CO)
What are some of the potential dangers from carbon monoxide (CO)?
-Is a toxic gas which is colourless and odourless
-it binds to heamoglobin and reduces the oxygen-carrying capacity of blood
-victims can lose consciousness and even die
What are the conditions needed for alkanes to undergo radical substitution to form a radical ?
-ultraviolet light
-or temperatures of about 300 degrees Celsius
What are Alkenes?
-they are unsaturated hydrocarbons that contain a C=C bond comprising of a pi bond and a sigma bond
-the pi bond holds the atom in position by restricting the rotation around the double bond
What is a pi bond?
-a sideways overlap of adjacent p-orbitals above and below the bonding C atoms
-they can only be made after a sigma bond has been formed
What is the bond angle and shape of an alkene?
-each bond angle repels by the same amount forming bond angles of 120 degrees resulting in a trigonal planar shape
Define an electrophile?
An electron pair acceptor
-e.g. positive ions and molecules with a positive region of charge
What is the reactivity of alkenes?
-alkenes are more reactive than alkanes
-as pi bonds have a lower bond enthalpy than sigma bonds so they are weaker, meaning in an alkene chemical reaction the pi bond will break first and react leaving a sigma bond between the 2 carbon atoms
-the double bond is an area of high electron density that will attract electrophiles
What is hydrogenation and what are the conditions?
-an addition reaction where hydrogen is added across the C=C bond
-CONDITIONS -a temperature of 150 degrees Celsius, a nickel catalyst
-gaseous hydrogen and an alkene are mixed then passed over the catalyst in a reaction chamber
-this saturates the alkene and an alkane is produced
What is halogenation?
-an addition reaction, where a halogen is added across the C=C bond- the alkene becomes saturated and a dihaloalkane is produced
What can halogenation be used for?
-this reaction can be used to test for saturation
-when bromine or iodine solution is mixed with a saturated compound (an alkane) no reaction occurs
-however when bromine is added to an unsaturated compound (an alkene) decolorisation happens as an addition reaction occurs
What is a hydration reaction?
-an addition reaction between a gaseous alkene and steam-used in industry to make alcohols
CONDITIONS- high temperatures (300 degrees Celsius), high pressure (65atm) and a phosphoric acid (H3PO4) catalyst
What is the addition of hydrogen halides?
-an addition reaction in which a hydrogen halide is added across the C=C bond
-this produces a haloalkane
-hydrogen halides e.g. HCl , HBr and HI are gases at room temperature , these reactants are bubbled through the alkene to cause a reaction
How can Markownikoff’s rule be used to predict the product when a hydrogen halide is added to an unsymmetrical alkene?
-it states that when H-X is added to an unsymmetrical alkene , the hydrogen becomes attached to the carbon with the most hydrogen atoms to start with
-because carbocations that have an alkyl group attached are more stable than those with hydrogen atoms attached
What happens during a polymerisation reaction?
-monomers have their pi bond broken
-the electrons from each pi bond make a sigma bond with a neighbouring carbon atom on a different monomer
-this connects the monomers chemically generating a saturated polymer with long carbon chains
What are the benefits of cheap oil-derived plastics counteracted with the problems for the environment of landfill?
BENEFITS: -they have many uses -clothing, materials in cars
-they are very stable
PROBLEMS:-due to the anaerobic conditions and lack of water in the large holes of landfill, the rate of decomposition is slow and many plastics are non-biodegradable
-if the waste does not break down it becomes a risk to wildlife
What are the benefits to sustainability by processing waste polymers by combustion?
-the chemical energy that is made can be used to drive turbines and generate electricity
-however this combustion releases carbon dioxide which is a greenhouse gas it can also release other polluting gases
-these gases can be removed by using gas scrubbers, where a base like CaO neutralises acidic gas
What are the benefits for sustainability by processing waste polymers by using them as organic feedstock?
-after waste plastics have been sorted into different types , a series of chemical reactions can be used to break plastic polymers up into small organic molecules
-this allows the recovered chemical to be used in other industrial reactions e.g. the production of plastics and other organic chemicals
What are the benefits to the environment of development of biodegradable and photodegradable polymers?
-reducing the dependency on finite resources
-alleviating problems from disposal of persistent plastic waste
What are biodegradable polymers?
-when a polymer like plant starch is mixed with an addition polymer
-these biodegradable polymers are affected by the action of microorganisms and environmental conditions , leading to decomposition
What is a bioplastic?
A material made from a renewable source that is biodegradable
What are photodegradable polymers?
-plastics that break down using energy with wavelengths similar to light
-they are either addition polymers with bonds within their structure that are weakened by absorption of light or they have an additive that is affected by light , which then weakens the bonds in the polymer
-once the polymer has been exposed to light it begins to break down and it is not possible to slow down the process
What is a disadvantage of photodegradable polymers?
-photodegradable plastics in landfill may not be exposed to sufficient light to degrade
What is a general formula?
The simplest algebraic formula of a member of a homologous series
What is a structural formula?
The minimal detail that shows the arrangement of atoms in a molecule
What is displayed formula?
The relative positioning of atoms and bonds between them
What is skeletal formula?
The simplified organic formula, shown by removing hydrogen atoms from alkyl chains, leaving just a carbon skeleton and associated functional groups
An alkene can have Cis/Trans isomers as long as:
-the carbon atoms on the double bond MUST be attached to TWO DIFFERENT GROUPS
-at least one of the groups must be the SAME on BOTH CARBON ATOMS on the double bond
How do you determine if it is a Cis or Trans isomers?
-look at the group which is the same on both sides of the double bond
-if the two of the same groups are on the SAME side of the molecule than it is a CIS isomer
-if the two of the same groups are on OPPOSITE sides of the molecule then it is a TRANS isomer
How do you use the Cahn-Ingold-Prelog (CIS) priority rules?
Used to identify the E and Z stereoisomers.
1- locate the carbon double bond and redraw it to show the substituents (the groups on both sides of the double bond)
2-focus on one carbon atom and assign the priority of each substituent based on its relative atomic number -the highest is given highest priority. Then assign priority of the second carbon atom
3-if the highest priority groups are on the SAME SIDE then the isomer is Z
If the highest priority groups are on DIFFERENT SIDES then the isomer is E
What is the mechanism for the radical substitution of chlorine and methane?Using UV radiation
What is the mechanism for the radical substitution of bromine and ethane using UV radiation?
What happens to the monomers during a polymerisation reaction?
-monomers have their π-bond broken
-the electrons from each π-bond make a σ-bond with a neighbouring carbon atom on a different monomer
-this connects the monomers chemically, generating a saturated polymer with long carbon chains
How do you work out the structure of a polymer from its monomer?
1- draw the monomer structure so that the C=C bond is the focus of the diagram
2-draw square brackets round the monomer
3-change the C=C to C-C and draw two lines extending from each C atom through the square brackets
4-add a subscript ‘n’
What is the general formula for Cycloalkanes?
CnH2n-2
What is the formula for an alcohol functional group and the suffix and prefix that you add for it?
Formula-OH
Prefix-hydroxyl
Suffix-ol
What is the formula for the functional group of an aldehyde and what is the suffix you add for it?
Suffix- al
What is the formula for a carboxylic functional group and what is the suffix ?
Suffix-oic acid
What are the prefixes you add for a haloaklane?
Fluoro-
Chloro-
Bromo-
Iodo-
What is the formula for a ketone and what is the suffix you add for it?
-suffix- one
