4.1 - basic concepts and hydrocarbons Flashcards
What is nomenclature?
The system of naming compounds
Hydrocarbons are made up of molecules that contain only hydrogen and carbon atoms. When you look at their structures, you can classify them as: (give 3 classifications and their definitions)
- aliphatic hydrocarbons: in which the carbon atoms are joined together in either straight (unbranched) chains or branched chains
- alicyclic hydrocarbons: in which the carbon atoms are joined together in a ring structure but are not aromatic
- aromatic hydrocarbons: in which there is at least one benzene ring in the structure
Define homologous series
A homologous series is a series of organic compounds that have the same functional group with successive members differing by CH2
Give the first ten prefixes of alkanes and alkenes
1) meth
2) eth
3) prop
4) but
5) pent
6) hex
7) hept
8) oct
9) non
10) dec
What are alkanes?
The simplest homologous series is the alkanes. They are aliphatic saturated hydrocarbons, so they contain only carbon and hydrogen joined by single covalent bonds.
What three rules do you need to consider when naming an organic compound?
stem - the main part of the name; generated by identifying the longest carbon chain or parent chain
suffix - the end of the name; identifies the most important functional group
prefix - the front part of the name; identifies the other functional groups and the carbon atoms they are attached to
Name the first ten alkyl groups (these are known as the stem)
1) methyl
2) ethyl
3) propyl
4) butyl
5) pentyl
6) hexyl
7) heptyl
8) octyl
9) nonyl
10) decyl
Define a saturated compound
Saturated compounds have only single bonds
Define functional group
A functional group is a group of atoms that is responsible for the characteristic chemical reactions of a compound
What four things should you remember when naming compounds?
1) numbers are used to indicate which carbon atom an alkyl group is joined to
2) dashes are used to separate numbers from words
3) commas are used to separate numbers
4) prefixes are written in alphabetical order using the smallest numbers possible to indicate which carbon atoms they are joined to
No number is needed when naming aldehydes because this functional group is always on a terminal (end) carbon atom. For organic compounds with more than one identical group, add…
- ‘di-‘ to show two of the same group
- ‘tri-‘ to indicate three of the same group
- ‘tetra-‘ to describe four identical groups
What is the general formula of alkanes?
CnH2n+2
Define general formula
A general formula is the simplest algebraic formula for a homologous series
Define display formula
A displayed formula shows the relative positions of atoms and the bonds between them
Define structural formula
A structural formula provides the minimum detail for the arrangement of atoms in a molecule
What five steps can you use to work out the empirical formula?
1) change the percentages to masses
2) calculate the number of moles in each element using: amount in moles = mass/RFM
3) divide by the smallest value
4) change the ratio to whole numbers
5) write the formula
You can use a three-step method to generate the molecular formula from the empirical formula and molecular mass. What are these three steps?
1) calculate the relative empirical mass using the empirical formula
2) divide the relative molecular mass by the empirical formula mass
3) multiply each atom in the empirical formula by the number calculated in step 2 and write the molecular formula
Define skeletal formula
a skeletal formula is a simplified structural formula drawn by removing hydrogen atoms from alkyl chains
Define unsaturated
Unsaturated organic chemicals contain at least one carbon-carbon double covalent bond
Define structural isomer
Structural isomers are compounds with the same molecular formula but different structural formulae
Define stereoisomers
Stereoisomers are organic compounds with the same molecular formula and structural formula but having a different arrangement of atoms in space
Define Cis-trans isomerism
Cis-trans isomerism is a type of E/Z isomerism in which the two substituent groups attached to both carbon atoms of the C=C bond are the same
Define E/Z isomerism
E/Z isomerism is a type of steeoisomerism caused by the restricted rotation around the double bond -two different groups are attached to both carbon atoms of the C=C double bond
Structural isomers are compounds with the same molecular formula but different structural formula. In what three ways can this happen?
- the alkyl groups are in different places
- the functional group can be bonded to different parts of the parent chain
- the functional group could be different
Define reaction mechanisms
Reaction mechanisms are the models that show the movement of electron pairs during a reaction
Define curly arrows
Curly arrows model the flow of electron pairs during reaction mechanisms
Define homolytic fission
Homolytic fission happens when each bonding atom receives one electron from the bonded pair, forming two radicals
Define radicals
Radicals are species with one or more unpaired electrons
Define heterolytic fission
Heterolytic fission happens when one bonding atom receives both electrons from the bonding pair
What happens in the initiation step and what conditions are required?
A free radical is created.
UV light or temperatures of about 300 degrees C are needed
