Organic Chemistry Flashcards
Organic chemistry
The chemistry of compounds containing CARBON.
Carbon forms many different compounds:
- Fuels
- Alcohol
- Drugs
- Biological molecules
Hydrocarbons
- The simplest type of organic compound
- Contains hydrogen and carbon ONLY
- Obtained from CRUDE OIL which is NON-RENEWABLE
Organic compounds
Can contain the following elements:
- Carbon
- Hydrogen
- Nitrogen
- Oxygen
- Phosphorus
Properties of Hydrocarbons
CARBON ALWAYS FORMS 4 COVALENT BONDS:
- It is found in group 14 and pairs its four outer electrons to obtain a full outer shell.
SATURATED:
- Hydrocarbons contain only SINGLE C-C bonds.
UNSATURATED:
- Hydrocarbons contain at least one DOUBLE C-C bond or a TRIPLE C-C bond.
ALICYCLIC:
- Hydrocarbons have CYCLIC structures ~ contain RINGS of carbon atoms.
- are not aromatic
ALIPHATIC:
- Hydrocarbons which are BRANCHED or
UNBRANCHED.
- CYCLIC hydrocarbons can also be aliphatic.
AROMATIC:
- Hydrocarbons which have at least one benzene ring in the structure.
- BOTH aliphatic and alicyclic hydrocarbons DO NOT contain BENZENE RINGS.
Alkanes
SATURATED hydrocarbons~ only contain single C-C bonds.
General formula ~ Cn H2n+2
Bond angle ~ 109.5 degrees
Functional group ~ C-C single bond ( It is usually this bond which breaks during chemical reactions)
Homologous Series
These are organic compounds which contain the SAME FUNCTIONAL GROUP and successive members differ by a -CH2 group.
Why do ALKANES form a homologous series?
SAME functional group :
- Single C-C bonds
- This leads to the members showing a SIMILAR CHEMICAL REACTIVITY.
Successive members differ by a -CH2 group:
- Leads to trends in PHYSICAL PROPERTIES
- BP of alkanes increases down the homologous series as the number of electrons and size of temporary dipole increases.
- This causes the strength of LONDON forces to increase.
- Require more energy to overcome.
Organic compounds are named according to the number of C atoms in their longest chain.
1 - meth
2 - eth
3 - prop
4 - but
5 - pent
6 -hex
7 - hept
8 - oct
9 - non
10 - dec
Steps to naming a BRANCHED alkane
Identify the longest chain of carbon atoms:
This gives the STEM name
Identify the number of carbon atoms in the SIDE-CHAIN:
This gives us the ALKYL group.
State the position of the alkyl group on the main chain:
Number from the end which produces the LOWEST possible number .
Alkyl group based on the number of carbon atoms on a branch
1 - methyl
2 - ethyl
3 - propyl
4 - butyl
5 - pentyl
Functional group
The part of an organic molecule which is responsible for its CHEMICAL REACTIONS.
Rules for naming compounds
- Look for the longest chain of carbon atoms.
- Find the main functional group ~ The following will take precedence over ALCOHOLS because the carbon has more bonds to oxygen:
- Aldehydes
- Ketones
- Carboxylic acids
The prefix becomes HYDROXY - Identify branches/ other functional groups
- Number the carbon atoms so that functional groups are on the lowest possible carbon atoms.
Putting the name together
- The name of the group has a number representing the carbon it is attached to.
- The side chains and functional groups are listed ALPABETICALLY.
- Two numbers written together are separated by a COMMA.
- A number and name are separated by a HYPHEN.
- When there is more than one of the SAME group we use ~ DI, TRI , TETRA
Empirical ,Molecular & general formula DEFINITIONS.
EMPIRICAL ~ the simplest whole number ratio of atoms of each element in a compound.
MOLECULAR ~ the actual number of each atoms of each element in a compound.
GENERAL ~ the simplest algebraic formula for a member of a homologous series.
The GENERAL and MOLECULAR formula of the following homologous series:
- Alkanes
- Alkenes
- Alkynes
- Cycloalkanes
- Alcohols
- Aldehydes
- Ketones
- Carboxylic acids
Alkanes:
GF ~ CnH2n+2
MF ~ CnH2n+2
Alkenes:
GF ~ CnH2n
MF ~ CnH2n
Alkynes :
GF ~ CnH2n-2
MF ~ CnH2n-2
Cycloalkanes:
GF ~ CnH2n
MF ~ CnH2n
Alcohols :
GF ~ CnH2n+1OH
MF ~ CnH2n+2O
Aldehydes:
GF ~CnH2nO
EF ~CnH2nO
Ketones:
GF ~ CnH2nO
MF ~ CnH2nO
Carboxylic acids :
GF ~ CnH2n+1COOH
MF ~ CnH2nO2
Displayed formula
Shows how each atom is BONDED to other atoms in the molecule.
It also shows the RELATIVE POSITIONS of each atom.
The COVALENT BONDS are shown.
Structural formula
This shows the ARRANGEMENT of atoms WITHOUT drawing the covalent bonds.
Skeletal formula
- The organic compound is shown as a ZIG ZAG
- Each POINT represents a CH2
- An END POINT represents a CH3
- The FUNCTIONAL GROUP extends from the carbon in which it lies.
Benzene
- First isolated by MICHAEL FARADAY in 1825.
Analysis of benzene found that:
- EF was CH
- Molecular mass was 78
- Formula of C6H6
August Kekule suggested in 1865 that benzene was:
- Planar
- Cyclic
- Had alternating double bonds and single bonds.
( Cyclohexa - 1,3,5 - triene )
- Benzene actually has DELOCALISED electrons above and below the plane of the carbon atoms .
- They are represented by a CIRCLE inside the hexagon.
Chemical Reaction
- Involves the MOVEMENT of electrons.
- When a chemical reaction takes place , bonds in the REACTANTS break and NEW bonds are formed in the PRODUCTS.
- A chemical reaction begins when one species ATTACKS another compound.
- The reaction begins with one of the THREE reactive attacking species:
- Nucleophile
- Electrophile
- Radical
How do we represent the movement of electrons?
- We use CURLY ARROWS
- The movement of PAIR of electrons is shown by a DOUBLE HEADED arrow drawn from a bond or a lone pair.
( HETEROLYTIC FISSION) - The movement of a SINGLE electron is represented by a SINGLE HEADED arrow.
(HOMOLYTIC FISSION)
HETERolytic Fission & HOMOlytic Fission
When a bond breaks and BOTH electrons go to ONE of the bonded atoms.
When a bond breaks and ONE electron goes to EACH atom.
Radical
Species with an UNPAIRED ELECTRON.
- Attack SINGLE and NON-POLAR bonds.
Electrophile
Electron pair ACCEPTOR.
- Has a positive charge or delta positive charge.
- Attacks electron rich areas such as C=C double bonds.
Nucleophile
Electron pair DONOR.
- Has a LONE PAIR or a NEGATIVE charge.
- Attacks electron deficient areas such as positive or delta positive regions.
THREE types of chemical reactions
ADDITION ~
- when two molecules react to form a single product.
- unsaturated molecule forms saturated molecule
SUBSTITUTION ~
- when an atom or group of atoms is replaced by another atom or group of atoms.
- 2 moles of reactant form 2 moles of product
ELIMINATION ~
- a reaction in which atoms of a singe molecule are removed from the organic molecule and not replaced by another atom or group of atoms.
- 1 mole of reactant is converted to 2 moles of product
- a saturated molecule forms an unsaturated molecule
Structural Isomerism
Structural isomers are molecules with the SAME molecular formula but DIFFERENT structural formula.
