Nomenclature & Isomerism

Question 1

What is a homologous series?

Answer 1

A family of chemicals with:
the same functional group
similar chemical properties
each successive member differs by one C atom

Question 2

What is an alkane?

Answer 2

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

Question 3

what is the bond angle of an alkane?

Answer 3

109.5

Question 4

What is fractional distillation?

Answer 4

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

Question 5

Reactions of alkanes

Answer 5

Combustion
Cracking
isomeration
reformation
free radical substitution

Question 6

what C range are fuel gases?

Answer 6

C1 to C4

Question 7

what C range are gasoline/ petrol?

Answer 7

C5 to C12

Question 8

what C range are kerosene?

Answer 8

C11 to C15

Question 9

what C range are diesel?

Answer 9

C15 to C19

Question 10

What are structural isomers?

Answer 10

Alkanes can exhibit structural isomerism

Molecules with the same molecular formula, but with different structural arrangements

Question 11

Step 1 naming alkane

Answer 11

Determine C longest chain

Question 12

Step 2 naming alkane

Answer 12

Number chain so side chain (substituent) gets lowest possible number

Question 13

Step 3 naming alkane

Answer 13

Determine number of C atoms in side chain (substituent)

Question 14

Step 4 naming alkane

Answer 14

Put it all together

Question 15

What are cycloalkanes?

Answer 15

Cyclic hydrocarbons
C formed in a ring
C atoms are singly bonded to other atoms

Question 16

Stem

Answer 16

No. of C atoms in longest chain bearing functional group

Question 17

Suffix

Answer 17

What functional group is present
position is annotated where in the C chain it is

Question 18

Prefix

Answer 18

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..

Question 19

What is an alkene?

Answer 19

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

Question 20

What is stereoisomerism?

Answer 20

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

Question 21

What is a geometric stereoisomer?

Answer 21

A stereoisomer with different physical properties

cis- substituents on the same side of double bond
trans- substituents on different side of double bond

Question 22

what is an alkyne?

Answer 22

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

Question 23

What is a heteroatom?

Answer 23

Any other element other than C or H

Question 24

How do halogens bind?

Answer 24

don’t use hybrid orbitals to bind with C
Bond through unhybridised p orbital

Question 25

What is an organic halide?

Answer 25

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

Question 26

Organic halide isomerism

Answer 26

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

Question 27

What is a chiral centre?

Answer 27

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

Question 28

Can chiral centres exist as isomers?

Answer 28

Exist as 2 optical isomers
mirror images of each other
non-superimposable

Question 29

What are optical isomers?

Answer 29

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

Question 30

reaction with plane polarised light

Answer 30

rotate the plane of light by equal amount
but in opposite directions
optical isomers or enantiomers
have different biological properties