Alkanes Flashcards
What is the name of the first alkane?
methane
What is the name of the second alkane?
ethane
What is the name of the third alkane?
propane
What is the name of the fourth alkane?
butane
What is the name of the fifth alkane?
pentane
What is the name of the sixth alkane?
hexane
What is the name of the seventh alkane?
heptane
What is the name of the eighth alkane?
octane
What is the name of the ninth alkane?
nonane
What is the name of the tenth alkane?
decane
What are the general characteristics of a homologous series?
All members can be represented by a single general molecular formula. The structure of each member differs by CH2 each time. Physical properties show a steady change with increasing molar mass. Adjacent members become more alike with increasing molar mass.
Define structural formula.
The minimal detail that shows arrangement of atoms
Define General formula.
The simplest algebraic formula of a member of a homologous series
Define displayed formula.
The relative positioning of atoms and the bonds between them
Define skeletal formula.
The simplified organic formula shown by removing hydrogen atoms leaving just a carbon skeleton
What is the general formula of an alkane?
CnH2n+2
What is the general formula for cycloalkanes?
CnH2n
Define empirical formula.
The simplest whole number ratio of atoms of each element present in a compound.
Define molecular formula.
The actual number of atoms of each element in a molecule.
Define homologous series.
A series of organic compounds that have the same functional group but with each successive member differing by CH2
Define the term functional group.
A group of atoms responsible for the characteristic reactions of a compound.
What does aliphatic mean?
A compound containing carbon and hydrogen joined together in straight chains, branched chains or non-aromatic rings.
Define the term structural isomer.
Two molecules that have the same molecular formula but a different structural arrangement.
True or false? Cycloalkanes react like an alkane.
True
What is combustion?
A chemical reaction where something burns in oxygen to release light and heat energy.
Give three possible sources of ignition.
Heat, friction, electricity.
Give two pieces of information about the way that hydrocarbons burn.
They burn relatively cleanly and they release a lot of energy.
What is the equation for full combustion?
Fuel + oxygen —> carbon dioxide + water
What products may be given off if incomplete combustion occurs?
Carbon + water, carbon monoxide + water, hydrocarbon + water.
What is the functional group of an alkene?
C=C
What is the functional group of an alcohol?
-OH
What is the functional group of a haloalkane?
-Cl -Br -I
What is the functional group of an aldehyde?
-CHO (double bond between carbon and oxygen.
What is the functional group of a ketone?
-C(CO)C- (double bond to oxygen on the middle carbon
What is the functional group of a carboxylic acid?
-COOH
What is the prefix/suffix of an alkene?
-ene
What is the prefix/suffix of an alcohol?
hydroxyl- -ol
What is the prefix/suffix of a haloalkane?
chloro- bromo- iodo-
What is the prefix/suffix of an aldehyde?
-al
What is the prefix/suffix of a ketone?
-one
What is the prefix/suffix of a carboxylic acid?
-oic acid
Which of these two conformations is the most stable? Why?
The first one because the hydrogen atoms can be the furthest apart from eachother.
What type of bonds join the carbon and hydrogen atoms in a hydrocarbon?
Covalent bonds.
True or false? The covalent bonds in a hydrocarbon are very strong and prevent the molecule of ethane breaking up into carbon and hydrogen again.
True
What is the name given to the forces that attract separate molecules of ethane to each other?
Intermolecular forces called London Dispersion forces.
What happenes to the bonds and forces when a liquid boils?
The weak intermolecular forces get broken allowing individual molecules to separate away from eachother to become a gas. The covalent bonds are still intact.
What is the boiling point of a liquid?
A measure of how much heat energy we need to overcome its intermolecular forces.
Fill in the blanks. Smaller hydrocarbons have _____ intermolecular forces between each molecule.
Fewer
Fill in the blanks. Smaller molecules require _____ heat energy to break the forces and turn the liquid into a gas.
Less
Fill in the blanks. Smaller hydrocarbons have a _____ boiling point than larger hydrocarbons
Lower
Explain why an alkane with side branches will have a lower boiling point than a straight chain alkane with the same number of carbon atoms.
An alkane with side branches will have a lower boiling point than a straight chain alkane with the same number of carbon atoms because there will be less points of contact between molecules which means that it is harder to induce a dipole and therefore there are less forces of attraction.
Describe the process of free radical substitution.
- Step 1 (initiation) - covalent bond in a bromine molecule is broken by hydrolytic fission. Each bromine atom takes one of the unpaired electrons forming two highly reactive radicals. Energy provided by UV light.
- Step 2 (propagation step 1) - a bromine radical reacts with the methane forming a methyl radical and a molecule of hydrogen bromide. CH4 + Br• → CH3• + HBr
- Step 2 (propagation step 2) - Each methyl radical racts with another bromine molecule forming bromomethane and a new bromine radical. CH3• + Br2 → CH3Br + Br•
- The two steps continue until two radicals collide
- Step 3 (termination) - Two radicals collide to form a molecule with all electrons paired. Number of possible termination steps. (Br• + Br• → Br2) (CH3• + CH3• → C2H6) (CH3• + Br• → CH3Br)
What is the name of this shape?
Trigonal planar
What is the name of this shape?
tetrahedral
