⚫️ Topic 6: Organic Chemistry Flashcards
How many bonds can a carbon atom form?
4 covalent bonds
What is the order of carbons?
1 - meth- 2 - eth- 3 - prop- 4 - but- (Pent-, hex-, hept-, oct-, non-, dec-, …)
What is a straight (or branched) chain of molecules called?
Aliphatic
What is a closed ring of molecules called?
Alicyclic
A cycloalkane will have the same general formula as an alkene
What does a saturated molecule mean?
Contains only C-C single bonds (contains as much hydrogen as possible)
What does an unsaturated molecule mean?
Has C=C double bonds (/triple) - (has room for more hydrogens)
What does a molecular formula mean?
Gives exact number of each atom present with all of the same atoms grouped together
Eg. C3H6O2 NOT C2H5COOH
What is a structural formula?
Written in groups of the bonds around each carbon atom (Displayed formula ‘displays’ it all out), but use skeletal formula most of the time (ends of lines = carbons)
What is a functional group?
An atom or group of atoms that gives the compound some distinctive and predictable (chemical) properties/ reactions
What is a homologous series and what are the features of it?
A family of chemicals with the same functional group which differ by CH2 from the next member
- similar chemical properties (eg. All alkanes form carbon dioxide and water when burnt completely in air)
- trends in physical properties (eg. Increase in boiling temp.)
- next member differs by CH2
- same general formula
What does nomenclature mean?
Naming organic compounds
What do you first look for when naming organic compounds?
The longest carbon chain - make sure to check every chain to find the longest (may not be horizontally)
(This goes at the end of the name)
This also contains the functional group (the lowest locant number should be used for functional group)
What is a locant number?
Shows positions of atoms or groups (methyl, ethyl, bromo, hydroxyl) - the numbers represent the carbon atoms in the longest chain that the atoms or groups are attached to (eg. 2-, 3-, 2,2-)
- the lowest locant numbers possible should be used
- remember di, tri if multiple of a group or atom
Then add this before the longest chain name, making sure in alphabetical order (eg. Ethyl before methyl)
If something is written with brackets (eg. CH3CH(CH3)CH(CH3)2) how would the displayed formula look?
The parts in brackets would be drawn coming off the sides of the central carbon chain (side chains) - remember carbon atoms need 4 bonds (4 lines coming off it)
What are the two types of isomers?
- structural isomers
- stereoisomers
What is a structural isomer?
A molecule with the same molecular formula, but a different structural formula. There are three different types:
- chain isomerism
- position isomerism
- functional group isomerism
What are the three different types of structural isomerism, and explain what they are, with properties?
- chain isomerism - carbon chain is different (eg. Straight chain and branched chain) — similar chemical properties, slightly different physical properties (eg. The more branching, the lower the boiling point)
- position isomerism - the functional groups are in different locations on the carbon chain, but same carbon skeleton + same functional group (eg. Propan-1-ol and propan-2-ol) — similar chemical + physical properties
- functional group isomerism - different functional group, but same molecular formula — different chemical + physical properties
What is stereoisomerism?
Compounds with the same molecular formula and structural formula, but with atoms arranged differently in 3D. The two types are geometric isomerism and optical isomerism
What are geometric isomers and why does it only occur in certain molecules?
(There are only ever two geometric isomers) Compounds with a C=C double bond with atoms/groups attached to it at different positions (switch the atoms or groups that are attached to ONE C around)
C=C double bond has restricted rotation - ‘freezes’ groups on either side of the bond. Single bonds can rotate, so geometric isomerism does not occur in alkanes.
ALSO,
However it does not occur in all alkenes - BOTH C atoms of the C=C must have two different groups/atoms attached
(Present with C=C in the middle and the other two bonds coming out of the ‘corners’)
How do you name geometric isomers?
- the group/ atom with the highest mass takes priority - look at atomic numbers of atoms directly bonded to each carbon - if the same, move to the next atom in the chain
- if priority values are opposite side: E
- if priority values are the same side: Z (zame zide)
When can you use cis/trans notation?
If the two priority groups in a molecule are the same
Z = cis
E = trans
What is crude oil and how is it involved with fractional distillation?
- obtained by drilling into the ground
- crude oil is a mixture of mostly alkanes of different chain lengths, and therefore different boiling points (which is what determines the fraction it will be in - short chain hydrocarbons have low boiling point so are at the top of the fractionating column [petrol, paraffin], long chain hydrocarbons have high boiling points so are at the bottom [bitumen]) (cool at top, hot at bottom)
- crude oil is heated as it enters the column - vapours rise and condense at their boiling point
Why is fractional distillation necessary?
(Alkane fuels are obtained from the fractional distillation, cracking and reforming of crude oil)
As a mixture, crude oil isn’t very useful, but the different hydrocarbons that make up the mixture (fractions) are useful - each fraction has different applications (eg. Heating, cooking, road surfaces)
After the fractional distillation process, how are the products made even more useful?
Cracking - some excess heavier fractions (long chain alkanes) are broken down into smaller, more useful compounds which are in higher demand (eg. petrol)
- produces a smaller alkane and one or more alkene molecules (which can be used to make plastics)
Conditions: high temp. (to vaporise?) + catalyst (Al2O3)
