Intro to organic Flashcards
Functional groups
The functional group of a molecule is the group of atoms that determines the chemical properties of the molecule. e.g.
Explain why carbon can form the basis for such a large number of compounds:
carbon atom can form four bonds - versatile
carbon- carbon bonds are strong (347 k3/mol)
c-h bonds are strong and non-polar - stable!
homologous series
groups of similar chemicals are called
homologous series. A homologous series is a family of compounds that have:
* the same functional group and general formula.
* similar chemical properties
Consecutive members of a homologous series:
* differ by a -CH2 - unit
* have a trend in physical properties
general formula
A general formula is an algebraic formula that can describe any member of a family of compounds.
Empirical formulas
An empirical formula gives the simplest whole number ratio of atoms of each element in a compound.
Molecular formulas
A molecular formula gives the actual number of atoms of each element in a molecule.
Displayed formulas
A displayed formula shows how all the atoms are arranged, and all the bonds between them.
structural formula
minimum detail needed to show an unambiguous structure
A structural formula shows the atoms carbon by carbon, with the attached hydrogens and functional groups.
- The formula is written from one end of the molecule to the other.
- Each “backbone” atom is written sequentially, followed by the atoms or groups attached to it.
- Branches in the chain are shown in brackets.
Skeletal formulas
Shows the carbon backbone and functional groups only
Rules for drawing skeletal formulae:
- Draw chains of atoms as zig-zags with 120° angles to show the shape of the molecule.
- Carbon atoms aren’t drawn: they are situated at the ends of bonds, and the junctions between bonds.
- Any hydrogen atoms attached to the carbon skeleton are missed off - along with the C-H bonds.
- All other atoms are drawn in, along with their bonds and the atoms attached to them.
Alkanes
Alkanes have the general formula C„H2n+2. Their names all end in -ane,
They’ve only got carbon and hydrogen atoms, so they’re hydrocarbons.
Every carbon atom in an alkane has four single bonds with other atoms. It’s
impossible for carbon to make more than four bonds, so alkanes are saturated.
Rules for naming organic compounds - branched alkanes
Alkenes and alkynes
Other functional groups
Halogens
Cycloalkanes
Cycloalkanes have a ring of carbon atoms with two hydrogens attached to
each carbon. Cycloalkanes have two fewer hydrogens than other alkanes
(assuming they have only one ring), so cycloalkanes have a different general
formula from that of normal alkanes (C,H2n), but they are still saturated.
Alkenes
An alkene is a hydrocarbon with a carbon-carbon double bond.
They have the general formula C,H2n. The carbons on either end of the double bond are only bonded to three atoms each, rather than the maximum of four. This means that they could form another bond, so they are unsaturated. This makes alkenes fairly reactive
Alcohols
Alcohols are organic molecules that contain the -OH, or hydroxyl, functional group. They have the suffix ol, and the general formula Cn H2n+1 OH. Alcohols can be reacted to give alkenes, and vice versa.
Aldehydes
In aldehydes, one of the end carbons has a double bond to an oxygen atom and a single bond to a hydrogen atom.
The suffix for aldehydes is -al. The general formula is written as R-CHO, where R is just an alkyl group or an H atom.
Ketones
Like aldehydes, ketones also contain the C=O bond, except it isn’t one of the end carbons. The general formula is written R-CO-R’.
Carboxylic acids
Carboxylic acids all contain the carboxyl functional group:
Its suffix is -oic acid. The general formula is written R-COOH
Amine
NH2 Functional; group
Nitrile
C triple bond with N functional group (CN)
Naming alkanes
The IUPAC system for naming organic compounds is the agreed international language of chemistry.
summary of key nomenclature
magic ‘e’
Isomerism
Isomers are compounds with the same molecular formula but with different arrangements of atoms.
The different types of isomerism that you need to know at A Level are summarised in the diagram below:
Structural isomers
These have the same molecular formula but with different arrangements of atoms within the molecule. In other words, they have a different structural formula.
Structural isomers - chain isomerism
Different arrangement of the carbon skeleton. Similar Chemical properties but different physical ones.
Structural isomers - Positional isomerism
Same Carbon Skeleton and functional group but the functional group is in a different place. Similar Physical and chemical properties.
Structural isomers - Functional group isomerism
Same molecular formula but different functional groups. Both chemical and physical properties are different
Stereoisomerism
These have the same molecular & structural formula and but have a different arrangement of atoms within space
Stereoisomerism - Geometric isomerism (E-Z isomerism)
Geometric isomerism involves compounds that contain a C=C double bond
why alkanes don’t also show geometric isomerism
More complicated molecules (and rules!)
Stereoisomerism - optical isomerism
The second type of stereoisomerism is optical isomerism. Optical isomers are also called enantiomers
These are non-superimposable mirror images of each other, and will be covered in detail in Year 13.
Types of Organic Reaction
There are three general types of reaction in organic chemistry which will also develop into reaction mechanisms (addition, substitution, elimination reactions). These involve the making and breaking of bonds using conventional rules.
organic mechanisms
In general:
1. If a covalent bond is made, a curly arrow is used to represent the movement of
to form the bond between the two atoms
2. If a covalent bond is broken, a curly arrow is used to represent the movement of
from the bond on to one of the atoms.
Addition reactions
2 species jopin together to make one molecule , usually accompanied by the breaking of a double bond.
Substitution reactions
One functional group of a molecule is swapped for a different one
Elimination reactions
One molecule breaks to form 2 molecules, usually accompanied by formation of a double bond
Types of bond breaking - Homolytic fission (homolysis)
A covalent bond breaks with each atom getting one electron from the bond. Free radicals formed.
Half arrows show movement of a single electron.
Types of bond breaking - Heterolytic fission (heterolysis)
A covalent bond is broken with one atom getting both of the bonding electrons
full arrows show movement of a pair of electron.
What is a free radical?
A species with an unpaired electrons
What is a carbocation?
An ion with a positive charge on a carbon atom
What is a carbanion?
An ion with a negative charge on a carbon atom
Nucleophile
A nucleophile is an electron pair donor. They often attack partially positive carbons
C delta+
Electrophiles
A electrophile is an electron pair acceptor. They often attack electron rich areas (C=C):
Free radicals
Substances with an unpaired electron. They react by pairing their electron which often generates other free radicals.
