intro to organic chemistry- 3.1

what bonding is in organic compounds?

• mainly covalent bonding and carbon forms 4 bonds to hydrogen, oxygen, nitrogen and halogens

• these bonds are significantly polar- the pair of electrons is not bonded equally

• organic compounds are carbon compounds excluding: CO, CO2, CO3

how many bonds can each atom make?

Atom	No. of bonds	Type of bonds
C	4	Single, double, triple
H	1	Single
F/Cl/Br/I	1	Single
O	2	Single, double
N	3	Single, double, triple
S	2	Single, double

what is displayed formula?

shows how the atoms in a molecule are joined together, 2D representation of a 3D molecule

H H H H H H

| | | | | |

H — C — C — C — C — C — C — H

| | | | | |

H H H H H H

what is skeletal formula?

shows how the atoms in a molecule are joined to each other but only shows the bond between the carbon atoms. Any other atom, apart from carbon and hydrogen are show as their displayed formula

what is structural formula?

shows the arrangement of atoms without the ‘sticks’

e.g. CH3CH2CH2CH3

what is a homologous series?

a series of chemically similar organs compounds that

• conform to the same general formula (different one for each of the series

• have the same functional group- chemical properties are similar

• different carbon chain length so each member differ by a unit of CH2

what are the alkanes?

methane- CH4

ethane- C2H6

propane- C3H8

butane- C4H10

pentane-C5H12

hexane-C6H14

what are the alkenes?

ethene- C2H4

propene- C3H6

butene- C4H8

pentene- C5H10

hexene- C6H12

how do you name organic compounds?

1. identify any side groups- methyl, ethyl, halogens etc.

2. if two or more of the same side groups are present, name with di-, tri-, tetra-, penta-,

3. if different side groups are present arrange in alphabetical order

4. commas between numbers and dashes between letters and numbers

   e.g. 2-chloro- 1,3- dimethylpentane

5. if there is a double bond present, it takes priority (so is named so the double bond is on the lowest carbon)

what are structural isomers?

compounds that have the same molecular formula but different structural formula.

what are chain isomers?

they have the same molecular formula but different chain lengths (different physical properties)

what are position isomers?

they have the same molecular formula but different position of the functional group along the chain (different but very similar physical properties)

what is the shape of an alkene?

planar with atoms all being on the same plane and the bond angle of the carbon- carbon double bond is 120

what are stereoisomers?

same molecular and structural formula but different spatial orientation i.e. different arrangement of atoms in 3D space

what are the two types of stereoisomers?

geometrical and optical isomer

what are the conditions for geometrical isomers?

double bond to restrict rotations

atoms or group of atoms on the same carbon of the double bond must be different

what is the Cahn, Ingold and Prolog convention?

a sequence of rules for identifying e/z isomers

1. compare atomic number of atoms directly attached to the stereo centre, the higher this value, the greater priority (bulky group)

2. if they are the same, consider atoms at a distance 2 from stereo centre

which one is the e- isomer and z- isomer?

Z - bulky group on the same side- cis

E- bulky group diagonally opposite- trans