Topic 10: organic chemistry

carbon

• the chemistry of carbon is much more extensive than that of any other element with many compounds of carbon. the macromolecules that build up life are made of carbon

  • 4 valence electrons, abundance and high bonding capacity

difference between O2 and O3

O2 is stronger than O3 and O2 absorbs more UV

Why does benzene undergo substitution more readily than addition?

resonance makes C_C bonds too strong to break easily

catenation

the fact that carbon atoms can join together to form chains and rings

fractional distillation

components in a chemical mixture are separated using their different boiling points.

Alkanes

a family of hydrocarbons

reactivity of alkanes, alkenes and alkynes

Alkanes are the least reactive, alkene is more reactive, and alkyne is the most reactive

Carbon always makes how many bonds?

4

How does hydrocarbon molecular size effect its state

larger hydrocarbons have more LDF making it more polarizable = Higher Melting/boiling points (more bonds need to be broken to boil)

Isomers

Different compounds that have the same molecular formula

Functional Groups

Atom/group of atoms that give the molecule its chemical properties. They are the reactive part of the compound

Homologous Series

A series of compounds that have the same functional group - Each member differs by a unit of CH2

How does melting point change when a CH2 group is added?

melting/boiling point increases as it now has more bonds to break through

Aliphatic

Structures of straight/ branched chains/ rings of carbon atoms

1. Alkanes

2. Alkenes

3. Alkynes

4. Cyclic

Alkanes

Carbons bonded by single bonds (sigma bonds) making them fully saturated hydrocarbons. very stable. CnHn+2

Alkenes

A molecule that has at least one double bond (pi bond) between two carbon atoms, resulting in an unsaturated hydrocarbon (not the maximum number of hydrogens are bonded to the carbon atom). Unstable/reactive. CnH2n

Alkynes

A molecule that contains at least one triple bond between carbon atoms, wrestling in an unsaturated hydrocarbon. CnH2n-2

Aromatic

Structures based on that of benzene. Essentially the functional groups are the benzenes

Benzene

• A ring of 6 carbon atoms that are bonded to one another with double and single bonds with a resonance structure C6H6

• -the electron in the double bond are shared equally among all the carbons

• Very stable molecule because of its resonance

• “Pi electrons are delocalized in its arrangement “

Geometric (cis-trans) Isomers

When the alkyl groups are found on the same side of the carbon then it’s cis and if it’s on opposite sides than it’s trans

Benezene’s with Halogen substituent Groups

just named as “halogen prefix”benzene

Benzoic acid

benzene with a carboxyl (COOH) substituent group

Phenol

Benzene with a hydroxyl (OH) substituent group

Aniline

Benzene with an ammonia substituent group

Toluene

Benzene with a methyl (CH2) substituent group

Benzene as a substituent

Sometimes in hydrocarbon chains benzene is treated as a substituent and it is simply named using “phenyl”

Alcohols

Functional group: hydroxyl
Naming: anol
Example: Ethanol
General Formula: CnH2n+1OH

Properties of Alcohols

More polar than hydrocarbons - as hydrocarbon chain gets longer it becomes more non-polar
Form hydrogens bonds because of the hydroxyl group
Higher melting/boiling points since it has hydrogen bonds

Hydroxyl Group

an OH group (hydroxide)

Types of alcohols

Primary Alcohol 1
o
: bonded to 1 carbon alkyl
Secondary Alcohol 2o: bonded to 2 carbon alkyl
Tertiary Alcohol 3
o
: bonded to 3 carbon alkyl

polyalcohol

Includes more than one hydroxyl group

Aldehydes

Functional group: aldehydes (carbonyl)
Suffix: anal
Example: Ethanal
General formula: RCHO

Aldehyde Properties

Lower melting/ boiling points than alcohols since they don’t have the OH group for hydrogen bonding
Also are less soluble in water than alcohols
However, C=O bond is polar so they are more soluble and have higher boiling and melting points than hydrocarbon

Ketones

Functional Group: Carbonyl
Suffix: anone
Example: Propanone
General formula: RC(O)R'

Properties of Ketones

Lower melting/boiling points and less soluble in water than alcohols
However, C=O bond is polar so they are more soluble and have higher boiling and melting points than hydrocarbon

Ether

R-O-R
If it’s not the priority it’s represented with “oxy”
always as a prefix

Ether properties

A polar C-O bond, however can’t form hydrogen bonds
More soluble and higher melting/boiling points than hydrocarbons 
Less polar and lower melting/boiling points than alcohols

Esters

R-C(=O)(-O)-R’ - Made with a carboxylic like group in the middle however the hydrogen atom is replaced with another carbon chain
Main chain suffix end is “oate”

Ester Properties

Since it has no hydrogen bonding it is less polar than alcohols and carboxylic acids but it is still more polar than ethers and hydrocarbons 
More soluble and have higher mp/bp point than ethers and hydrocarbons but less soluble and lower mp/bp than alcohols and carboxylic acids (as an aqueous solution)

Amines

R-C-N-R’ - A carbon group bonded to a nitrogen (the nitrogen group can be bonded to up to two hydrocarbon chains or 2 hydrogens) - Functional group is NH2
Main chain suffix end is “amine”

Amines properties

SMALL amines are soluble in water as N-C bonds are polar
Higher mp/bp than hydrocarbons but because it’s less polar than O-C groups it is lower than alcohols

Types of amines:

Primary Amine 1
o
: 1 hydrocarbon chain 
Secondary Amine 2
o
: 2 hydrocarbon chains
Tertiary Amine 3
o
: 3 hydrocarbon chains

Amides

R-C(=O)(-N)-R’ - Similar to an ester but has an N instead of a single bonded O - Functional group is CONH2
Main chain suffix end is “amide”

Amide Properties

Smaller amides are water soluble as C=O is polar and forms hydrogen bonds with N
Higher mp/bp than ketones/aldehydes but a lower polarity than carboxylic acids
When maximum number of hydrogens are bonded to the amide it has a higher boiling point because it now has more hydrogen bond

Free radical substitution - 3 steps

Initiation
Propagation
Termination

Free Radical Substitution Step 1: Initiation

The making of a free radical (1 reaction)
Splits the electron equally, both atoms get one of the previously shared electrons - Forming the free radicals with the divided atoms

Heterolytic Fission

Splits the electron unevenly, one atom gets all the previously shared electrons

Homolytic Fission

Splits the electron equally, both atoms get one of the previously shared electrons
Written as X•

Free Radical Substitution Step 2: Propagation

The radical swapping around until the compound and the radical form another compound (2 reactions)
Radical takes hydrogen from the hydrocarbon forming a free radical hydrocarbon
Then the free radical hydrocarbon reacts with an element (that was originally the free radical from the initial step) and forms a compound with it and there is now an extra free radical of the original free radical

Free Radical Substitution Step 3: Termination

Shows all the radicals combining to form their respective compounds (3 reactions)

Overall reaction

the radicals original compound + the hydrocarbon → (catalyst of UV) hydrocarbon with the element radical + the hydrogen and the element radical

Bond Order

NHumber of chemical bonds between a pair of atoms - represents it’s stability
Number of covalent bonds divided by the number of atoms involved in the compound

Relationship between bond order and bond length

Bond order and bond length are inversely proportional to each other: as bond order increases bond length decreases
bond length which tells us how strong it is: Smaller bond lengths means it is a stronger bond and vice-versa

Catalysis of O2 in Ozone depletion

O
2
divides into two oxygen free radicals
Bond order of 2 → longer bond length → Weaker → less energy needed to break 
Only needs UV-C

Catalysis of O3 in Ozone depletion

O
3
divides into 1 oxygen free radical and then an oxygen compound 
Bond order of 1.5 -> Shorter bond length → stronger → more energy needed to break
Needs UV-B

Chlorofluorocarbons

Stable compounds that break down when it absorbs UV radiation → forms free radicals
destroys the ozone molecules when it is broken down by the UV light

What can prevent the destruction of the ozone?

These reactions can stop when the free radicals of NOx and CFCs collide together and form their own compound

Polymers

Molecules with many repeating identical parts
Made up of monomers 
Unreactive

Natural Polymers made of

DNA, Proteins, oils, fats etc

Monomers

Building blocks of polymers
Extremely reactive

Benefits of polymers

Cheaper to produce, and are chemical and biological UNREACTIVE
Have many properties

Polymer Formation: Addition Reactions

Involving an alkene monomer - Producing a long alkane chain 
Double bonds break and then a bond that is adjacent to the monomers form on BOTH sides of the original monomer

Different o=polymers made from addition reactions

Polyethylene (made from a chain of ethylene) ← Ethene
Polypropylene (made from a chain of propylene) ← Propene
Polyvinylchloride 
Polystyrene (made from a chain styrene) ← Phenylethene 
Teflon

Polymer formation: Condensation Reactions

Involves the condensation of one or two monomers with functional groups 
Producing amides and esters and water

Condensation Reactions

, a condensation reaction is a type of chemical reaction in which two molecules are combined to form a single molecule, usually with the loss of a small molecule such as water. If water is lost, the reaction is also known as a dehydration synthesis

Alcohol

Functional group: hydroxyl Naming: anol Example: Ethanol General Formula: CnH2n+1OH

Ether

Functional group: ether Suffix: oxy alkane Example: Methoxy Propane General formula: ROR'

Carboxylic acid

Functional group: Carboxylic acid Suffix: anoic acid. Example: Ethanoic Acid General formula: RCOOH. OH groups make these even more polar than other functional groups, so very soluble in water very high melting/boiling points

Ester

Functional group: Ester
Suffix: alkyl anoate
Example: Methyl Propanoate
General formula: RCOOR'

Amine

Functional group: Amine Suffix: anamine Example: Ethanamine General Formula: RNH2

Amide

Functional Group: Amine Suffix: anamide Example: Ethanamide General Formula: RC(O)NH2

alkene/alkyne colour change in bromine water

orange→ colourless

alkane colour change in bromine water

no colour change