Introduction to organic chemistry Flashcards
What does ‘organic’ mean?
Things to do with living beings
What is special about Carbon?
Carbon can form rings and very long chains, which may be branched
How can carbon form rings and chains?
- It has four electrons in its outer shell, so it forms four covalent bonds
- carbon-carbon bonds are relatively strong and non-polar
How strong are carbon-carbon bonds?
347 kJ mol-1
What chains form the skeleton of most organic compounds?
Hydrocarbon chains formed by fairly strong carbon-hydrogen bonds
How many electrons does carbon have in its outer shell?
8
What is the general suffix for compounds with a triple bond?
-yne (e.g. EthYNE)
What is the “empirical formula”?
The empirical formula is the simplest ration of the atoms of each element present in a compound
What is the molecular formula?
It is the formula that shows the actual number of atoms of each element in the molecule
What three factors is the molecular formula found from?
- the empirical formula
- the relative molecular mass of the empirical formula
- the relative molecular mass of the molecule
What is the structural formula?
This formula shows the unique arrangement of atoms in a molecule in a simplified form, without showing all the bonds
What is the structural formula for ethane?
CH3CH3
How are branches in carbon chains shown in the structural formula?
In brackets
What is different about the skeletal formulae?
In skeletal notation, carbon atoms are not drawn at all. Straight lines represent carbon-carbon bonds.
What is assumed when drawing the skeletal formula of a compound?
Each carbon is assumed to form enough C-H bonds to make a total of 4 bonds
What are the bond angles in an unbranched alkane chain?
109.5 degrees
What does the “root” of a chain mean?
It tells us the longest unbranched hydrocarbon chain or ring
What is the prefix for a side chain with two carbons?
Ethyl (C2H5-)
What is different about the prefix of ring molecules?
They have the additional prefix “cyclo”
What are functional groups?
Reactive groups attached to hydrocarbon chains
What is the general functional group for an alcohol?
R-OH
What is a lo and used for?
To tell us the position of any branching in a chain and the position of any functional group
What are structural isomers?
They have the same molecular formula but different structures
If a chain has more than one functional group, what order do you write the substituting groups?
Alphabetical
How do you show that you have more than one of the same substituting group?
By adding prefixes such as di- , tri- , and tetra-
What is a homologous series?
It is a family of organic compounds with the same functional group but different carbon chain length
Name 5 features of a homologous series:
- they have a general formula (e.g CnH2n+2)
- each member of the series differs from the next by CH2
- the carbon chain length has little effect on the chemical reactivity of the functional group
- the length of the carbon chain affects physical properties like MP and solubility
- chain branching generally reduces melting points because the molecules pack together less well
What are isomers?
They are molecules that have the same molecular formula but have a different atom arrangement
What three things can structural isomers have?
- the same functional group attached to be main chain at different points (position isomerism)
- functional groups that are different (functional group isomerism)
- a different arrangement of the carbon chain (chain isomerism)
What is position isomerism?
Where the functional group is attached to the main chain at different points
What is functional group isomerism?
Where there are different functional groups
What is chain isomerism?
Where the hydrocarbon chain is arranged differently
What does the existence of isomers make difficult?
The identification of an unknown organic compound as there may be a number of compounds with different structures but the same molecular formula
What is Stereoisomerism?
Where two (or more) compounds have the same structural formula. They differ in the arrangement of the bonds in space
What are the two types of Stereoisomerism?
- E-Z isomerism
* optical isomerism
What does E-Z isomerism tell us?
The positions of substituents at either side of a carbon-carbon double bond.
What does the ‘Z’ mean in Stereoisomerism?
That the substituents are on the same side of the bond (cis)
What does the ‘E’ of E-Z isomerism mean?
That the substituents are on opposite sides of the bond (trans)
What can substituted groups joined by a single bond do?
Rotate around the single bond
What does the rotation around these single bonds mean?
That there are no isomers
What are Z- and E- isomers?
They are separate compounds and are not easily converted from one to another
What is life on our planet based on?
Carbon
