Nomenclature & Isomerism Flashcards
What is a homologous series?
A family of chemicals with:
the same functional group
similar chemical properties
each successive member differs by one C atom
What is an alkane?
A saturated hydrocarbon
Cn H2n+2
C atom has tetrahedral geometry- bond angle 109.5
sp3 hybridised C atoms
Non-polar as similar electronegativites between c and h
van der Waals forces
what is the bond angle of an alkane?
109.5
What is fractional distillation?
separation of crude oil dependent on individual products boiling points
chain length of hydrocarbon increases, boiling point increases
gas -> liquid -> solid
chain length increases, more points of contact between molecules so more van Der Waals
Reactions of alkanes
Combustion
Cracking
isomeration
reformation
free radical substitution
what C range are fuel gases?
C1 to C4
what C range are gasoline/ petrol?
C5 to C12
what C range are kerosene?
C11 to C15
what C range are diesel?
C15 to C19
What are structural isomers?
Alkanes can exhibit structural isomerism
Molecules with the same molecular formula, but with different structural arrangements
Step 1 naming alkane
Determine C longest chain
Step 2 naming alkane
Number chain so side chain (substituent) gets lowest possible number
Step 3 naming alkane
Determine number of C atoms in side chain (substituent)
Step 4 naming alkane
Put it all together
What are cycloalkanes?
Cyclic hydrocarbons
C formed in a ring
C atoms are singly bonded to other atoms
Stem
No. of C atoms in longest chain bearing functional group
Suffix
What functional group is present
position is annotated where in the C chain it is
Prefix
Position and identity of any substituents
Side chains in alphabetical order
numbers sep by -
if identical side chains appear more than once get the prefix di, tri etc..
What is an alkene?
An unsaturated hydrocarbon
Cn H2n
Functional group of C=C
a sigma and pi bond
More reactive than the equivalent alkane as the pi bond is weaker than the sigma bond
What is stereoisomerism?
Alkanes have free rotation around C-C
Alkene have no free rotation around C=C, but can exhibit stereoisomerism
Molecules with same structural formula but have a different arrangement of atoms within space
Cant change each isomer by free rotation
can with breaking bonds
Cis and trans can interconvert but the double bond must break
What is a geometric stereoisomer?
A stereoisomer with different physical properties
cis- substituents on the same side of double bond
trans- substituents on different side of double bond
what is an alkyne?
hydrocarbon chain with a triple bond present
Cn H2n-2
Have a sigma bond and 2 pi bonds
More reactive than equivalent alkene as the second pi bond is weaker than the first pi bond
What is a heteroatom?
Any other element other than C or H
How do halogens bind?
don’t use hybrid orbitals to bind with C
Bond through unhybridised p orbital
What is an organic halide?
A halogenoalkane.
Cn H2n+1 X
Done have to be alkane based
Can be polar due to difference in electronegativities between C and X
C is always delta positive
Organic halide isomerism
can exhibit structural isomerism
both chemical and physical properties are different
can exhibit geometric stereoisomerism
physical properties are different
can exhibit optical stereoisomerism
the 2nd C is the chiral centre
What is a chiral centre?
A central C atom bonded to 4 different R groups
cannot be C bound to 2H
cannot be a symmetrical centre
cannot be C double bonded to another atom or C in aromatic ring
Can chiral centres exist as isomers?
Exist as 2 optical isomers
mirror images of each other
non-superimposable
What are optical isomers?
2 molecules with the same chemical and structural formulae, but different spatial arrangements of the atoms
Have identical physical properties except interactions with plane polarised light
reaction with plane polarised light
rotate the plane of light by equal amount
but in opposite directions
optical isomers or enantiomers
have different biological properties
