intro to organic chem [O1] PAPER 2

Question 1

what are structural isomers?

Answer 1

molecules with the same molecular formula, but different structural formula

Question 2

what are stereoisomers?

Answer 2

molecules with the same structural formula, but different arrangement of atoms in space

Question 3

state and define the three types of structural isomerism

Answer 3

• functional group - same molecular formula, different functional group
• chain - same molecular formula, different C chain
• positional - same molecular formula and functional group, different position of functional group

Question 4

characteristics of a homologous series?

Answer 4

• same molecular formula
• same functional group
• chemically similar
• gradation in physical properties as Mr increases

Question 5

what does an E isomer look like?

Answer 5

priority groups are on opposite sides of the C=C, and one on each C

X = priority group

Question 6

what does a Z isomer look like?

Answer 6

priority groups are on the same side of the C=C, and one on each C

X = priority group

Question 7

would this exhibit E/Z isomerism?

Answer 7

no, since two identical groups are attached to one of the Cs in the C=C

Question 8

how would you determine if the following compound is an E or Z isomer, hence its full IUPAC name using the CIP priority rules?

Answer 8

• consider the groups attached to the right-hand C of the C=C, so Y and Z
• consider the atomic number of the atoms from Y and from Z attached to the C
• if the atom attached from group Y has a larger atomic number than the atom attached from group Z, Y takes priority (or vice versa)
• if the atomic numbers of both atoms attached to the C are the same, consider the atoms one bond further away from the C and look at these atomic numbers instead
• if the highest priority groups are on the same side of the C=C, it is a Z isomer (if not, then E)

e.g. the full IUPAC name of the following is Z-1-chloro-2-methyl-but-2-ene:

Question 9

what is the empirical formula of a molecule?

Answer 9

simplest whole number ratio of atoms of each element in a compound

Question 10

what is the molecular formula of a molecule?

Answer 10

the total number of atoms of each element in a compound

Question 11

what is E/Z isomerism?

Answer 11

• a type of stereoisomerism
• molecules have the same structural formula, but different arrangement of atoms in space due to the lack of rotation around the C=C
• different groups attached to each C in the double bond

Question 12

what do structural formulae show?

Answer 12

the arrangement of atoms in the molecule, but not all the bonds between them

e.g. CH3CH2COCH3

Question 13

what do skeletal formulae show?

Answer 13

• used for organic compounds
• lines represent bonds between atoms
• C and H (if attached a C) aren’t written down - each new line thing means there’s another C
• any other atom is written out and the line from the C it is attached to is slightly shorter

e.g. this is CH3CONH2

Question 14

what do displayed formulae show?

Answer 14

show all bonds between all the atoms in a compound

e.g. methylamine