introduction to organic chemistry (3.3.1)

Question 1

what is molecular formula?

Answer 1

the actual number of atoms of each element in a compound eg. ethene - C2H4

Question 2

what is empirical formula?

Answer 2

the simplest whole number ratio of atoms of each element in a compound eg. butane - C2H5

Question 3

what is structural formula?

Answer 3

how the atoms in a molecule are arranged, but not all the bonds are shown eg. ethene - CH2=CH2

Question 4

what is displayed formula?

Answer 4

how the atoms in a molecule are arranged with all of the bonds shown eg. butanoic acid

Question 5

what is skeletal formula?

Answer 5

when only the carbon-carbon bonds are shown (using lines - each point represents a C atom), along with bonds to and atom labels for any atoms that aren’t C or H eg. butanoic acid

Question 6

what is general formula?

Answer 6

the simplest algebraic formula for a member of a homologous series eg. alkanes - CnH2n+2

Question 7

what is a functional group?

Answer 7

a group of atoms responsible for the chemical reactions of a particular compound eg. carboxylic acids - COOH

Question 8

what is a homologous series?

Answer 8

a series of organic compounds with the same functional group, but each successive member has an additional -CH2

Question 9

what are the characteristics of a homologous series?

Answer 9

they have the same general formula and functional group, similar chemical properties and a gradual trend in physical properties

Question 10

what are the rules for naming molecules following the IUPAC guidelines?

Answer 10

1. find the longest continuous chain of C atoms and apply a prefix based on the number of C atoms (meth-, eth-, prop- etc)
2. if there is a ring of C atoms, add cyclo as well
3. if there are any C=C bonds, use the suffix -ene, if not use -ane
4. number the position of the carbon atoms from one end of the chain, giving C=C bonds, functional groups or side chains the lowest possible number
5. if there are multiple side chains or functional groups, arrange the prefixes alphabetically ie. bromo- comes before chloro-
6. if there is more than one of the same group, use di- for 2, tri- for 3, tetra- for 4 etc
7. give the position of every group, numbering from end of the C chain so the lowest possible numbers are used (if there is a C=C bond, start from the end which gives these 2 C atoms the lowest possible number)
8. separate numbers and letters with - , and numbers with ,

Question 11

what does the vertical line in this skeletal structure represent?

Answer 11

methyl groups (2 - one on each side of the C atom)

Question 12

what does it mean if there is a CH3 group branching off a C atom at the end of a chain of C atoms?

Answer 12

the CH3 might not be a methyl group - it may be another C atom which is part of the main chain but has been shown as a branch (so don’t add methyl group to name)

Question 13

what would the name of this molecule be?

Answer 13

2-methylhexane

Question 14

what would the name of this molecule be?

Answer 14

1,2-dibromo-1-chlorobutane

Question 15

what would the name of this molecule be?

Answer 15

2-bromo-4-methylpent-2-ene

Question 16

what would the name of this molecule be?

Answer 16

2-methylhex-3-ene

Question 17

what is the definition of a structural isomer, and what are the three types of structural isomer?

Answer 17

when two compounds have the same molecular formula but a different structural formula
chain isomer, position isomer, functional group isomer

Question 18

what are chain isomers?

Answer 18

molecules with the same molecular formula but a different arrangement of carbon atoms in the main chain eg. pentane and dimethylpropane

Question 19

what are position isomers?

Answer 19

molecules with the same molecular formula but the functional group in a different position in the molecule eg. pent-1-ene and pent-2-ene

Question 20

what are functional group isomers?

Answer 20

molecules with the same molecular formula but different functional groups eg. cyclopropane and propene

Question 21

what is stereoisomerism?

Answer 21

when two compounds have the same molecular formula and structural formula, but a different arrangement of atoms and bonds

Question 22

what is E-Z isomerism?

Answer 22

a type of stereoisomerism which occurs as a result of restricted rotation about a planar carbon-carbon double bond

Question 23

what are E isomers?

Answer 23

E = entgegen (german for opposite)
they are when the priority groups are next to each other on the same side of the molecule

Question 24

what are Z isomers?

Answer 24

Z = zusammen (german for together)
they are when the priority groups are opposite each other on different sides of the molecule

Question 25

what are the two requirements for E-Z isomers to exist?

Answer 25

1. there must be a C=C double bond 2. each C atom must have 2 different groups attached

Question 26

what are the Cahn-Ingold-Prelog (CIP) priority rules for determining whether E-Z isomers are E or Z?

Answer 26

1. consider the two groups joined to the left hand carbon of the C=C bond 2. if the 1st atom of the two groups bonded to the C are different, the atom with the highest Ar takes priority 3. if the 1st atom of the two groups bonded to the C are the same, for both groups you need to work your way across from the 1st atom until you find two that are different 4. out of the two atoms that are different, the one with the highest Ar takes priority 5. repeat for the right hand carbon of the C=C bond 6. if the two highest priority groups are on the same side of the C=C bond, the isomer is Z if the two highest priority group are on opposite sides of the C=C bond, the isomer is E

Question 27

what can mechanisms be used for?

Answer 27

to explain the reactions of organic compounds - they show the movement of electrons during chemical reactions

Question 28

what is the unpaired electron in a free radical represented by?

Answer 28

a dot

Question 29

when does the free radical substitution mechanism occur?

Answer 29

when an alkane and a halogen react together in UV light

Question 30

what are the features of free radicals?

Answer 30

they are highly reactive and have an unpaired electron

Question 31

what would the balanced equations for the steps in a free-radical mechanism with propane and bromine be?

Answer 31

initiation: Br2 -> (UV light) Br. + Br. propagation: 1- Br. + CH3CH2CH3 -> HBr + CH3C.HCH3 2- Br2 + CH3C.HCH3 -> CH3CHBrCH3 + Br. overall- Br2 + CH2CH3CH2 -> HBr + CH3CHBrCH3 termination: Br. + Br. -> Br2 CH3C.HCH3 + CH3C.HCH3 -> CH3CHCH3CH3CHCH3 Br. + CH3C.HCH3 -> CH3CHBrCH3

Question 32

what is an asymmetric carbon atom?

Answer 32

a carbon atom bonded to four different types of atoms or groups of atoms

Question 33

how is the formation of a covalent bond shown using mechanisms?

Answer 33

shown by a curly arrow starting from a lone electron pair, or from another covalent bond

Question 34

how is the breaking of a covalent bond shown using mechanisms?

Answer 34

shown by a curly arrow starting from the bond