3.1 Organic Compounds Flashcards
alkanes
alkenes
halogenoalkanes
alcohols
primary, secondary, tertiary alcohol
primary - carbon atom of hydroxyl group attached to 1 alkyl group
secondary - carbon atom of hydroxyl group attached to 2 alkyl group
tertiary - carbon atom of hydroxyl group attached to 3 alkyl groups
carboxylic acids
take priority, use carbon from this as C1
aldehydes
ketones
esters
The compound is an ester, which is formed when a carboxylic acid reacts with an alcohol.
naming esters
how to name compounds
- find longest carbon chain
- The suffix (or prefix) of the name depends on the main functional group of the molecule
3.Number the carbon atoms in the chain so that the functional group (or side chain in an alkane) has the lowest possible number.
4.A side chain or secondary functional group is added as a prefix at the beginning of the name.
5.Common prefixes are methyl for a -CH3 group, ethyl for a -C2H5 group and chloro for a -Cl group. The prefixes are listed in alphabetical order. For example, ethyl comes before methyl.
6.If more than one identical side chain or functional group, use di- for 2, tri- for 3 and tetra- for 4.
7.Commas are put between numbers (e.g. 2,3), and dashes are put between numbers and letters (e.g. 2-methyl).
empirical formula
simplest whole number ratio of atoms of each element in a compound. The empirical formula may also be the molecular formula of the compound, or the molecular formula could be any multiple of the empirical formula
molecular formula
actual number of atoms of each element in a molecule. This does not show the functional group of a compound.
count and add together all carbons and hydrogens even if in side chain
displayed formula
shows all the atoms, and the bonds linking them, in the compound. This clearly shows the functional group present and would be used when considering a reaction mechanism.
skeletal formula
shows the bonds of the carbon skeleton as well as any functional groups. The carbon and hydrogen atoms that are part of the main carbon chain aren’t shown. It can reduce confusion when complex molecules are being considered and is widely used in research.
skeletal
ethyl
-C2H5
skeletal
methyl
saturated
only contains single bonds
unsaturated
carbon carbon double bond
homologous series
family of compounds with different chemiscal properties
differ by CH2
functional group
responsible for molecules chemical properties
hydrocarbon
compound containign carbon and hydrogen
carbon
can form large number of compounds
4 electrons in the outer shell
each carbon can form 4 covalent bonds
can form single, double or triple bonds
three types of hydrocarbon
aliphatic
alicyclic
aromatic
aliphatic hydrocarbon
carbon atoms joined in unbranched (straigt) or branched chains
alicyclic hydrocarbon
carbon atoms are joined to each other in ring (cyclic) structures
aromatic hydrocarbon
some or all of carbons are found in benzene ring
benzene ring
ring of 6 carbons with one hydrogen atom attached
Aliphatic Hydrocarbons (three homologous series):
alkanes
alkenes
alkynes
Alkanes
contain single carbon to carbon bonds
Alkenes
contain at least one carbon double bond
alkynes
contain at least one triple carbon to carbon bond
name indication:
stem
prefix
suffix
stem - number of carbon atoms in longest chain
prefix - indicates presence of side chin or functional groups
suffux - after stem indcates functional group
naming aliphatic alkanes
- suffix - ane
- longest chain of carbon atons
- side chains (alkyl groups), name of alkyl group is added to prefix
- number before alkyl groups show position on parent chain
eg 2,2-dimethlybutane
multiple side chains
two - di
three - tri
four - tetra
eg di methyl
naming alicylic alkanes (cyclic)
use prefix cyclo
naming alkenes
- choose suffix (alkenes use -ene)
- longest carbon cahin
- identify double bond (list smallest number when naming)
eg pent-2-ene
naming compounds with a functional group
- longest carbon chain
- identify functional groups of alkly side chains
- number alkly groups and functional groups to indicate position on longest unbranched chain
general formula of:
alkanes
general formula of:
alkenes
general formula of:
alcholos
general formula of:
carboxylic acids
general formula of:
kentones
Structural isomers
compounds with the same molecular formula but different structural formulae, i.e. the way the atoms are arranged.
3 types:
Chain isomerism
Positional isomerism
Functional group isomerism
Chain Isomerism
carbon chain of the molecule is arranged differently
straight chain - carbons have no brances, count carbons and hydrogens and draw simply look at pentane for eg
Positional isomerism
carbon skeleton and the functional group are the same, but the functional group is attached to a different carbon atom.
Functional group isomerism
This occurs when the functional group in the compounds is different.
are the following isomers?
Name them
butan-2-ol
hydrocarbons forces
Hydrocarbons only have induced dipole-induced dipole or van der Waals forces between their molecules
so their intermolecular forces are very weak.
what are Van der Waals forces
(van der Waals forces), which are the weakest type of intermolecular forces.
This results in a low boiling point.
act between the surfas of the molecules
The more surface there is in contact, the stronger the forces.
As the chain length gets longer, the surface contact between the molecules gets bigger;
as a result, it takes more energy to overcome the van der Waals forces
and the boiling (and melting) temperatures increase.
Graph to show how boiling temperature of alkanes increase as chain length increases
state of short vs longer hydrocarbons
small hydrocarbons are gases at room temperature,
larger hydrocarbons are liquids and the largest are solids.
branched chain alkanes boiling point vs straight chain isomer
branched-chain alkane, lower boiling point than its straight-chain isomer.
Branched can’t pack closely together so they have smaller molecular surface areas.
The more branches an isomer has,
less surface contact there is between molecules
means weaker van der Waals forces between molecules
so less energy is needed to separate them
lower boiling temperature.
Effect of functional group on boiling point
Explain differences in boiling point
In butane, the only intermolecular forces are induced dipole – induced dipole forces. - no hydrogen bonding between molecules
Chloroethane has a polar Cδ+ – Clδ- which gives rise to a permanent dipole. Therefore, there are extra dipole – dipole forces between the molecules and more energy is needed to break these bonds.
In propan-1-ol, hydrogen bonds occur between the -OH groups. Since hydrogen bonds are the strongest intermolecular forces, even more energy is needed to break them, resulting in the largest boiling temperature.
Effect of functional group on solubility
Since hydrogen bonds are the most significant intermolecular forces between water molecules, organic compounds that can form hydrogen bonds with water will dissolve.
Compounds like butane and chloroethane cannot dissolve in water because they only form induced dipole – induced dipole or dipole – dipole forces between molecules and are not able to form significant attractions with the water molecules.
alcohols and carboxylic acids have –OH groups that can form hydrogen bonds with water. However, solubility decreases as chain length increases, so only the smaller alcohols and carboxylic acids are soluble.
**
larger alcohols and carboxylic acids have longer hydrocarbon chains** which are hydrophobic. At about four or five carbons, the hydrophobic effect is so large that the compound is no longer soluble.
Electrophiles
An electrophile is an electron-deficient species that can accept a lone pair of electrons.
Most electrophiles are positively charged or have an atom that carries a partial positive charge. Examples are H+, NO2+ and Hδ+–Brδ-. Na +
Nucleophiles
A nucleophile is a species with a lone pair of electrons that can be donated to an electron-deficient species.
Many nucleophiles are negatively charged, formed by gaining electrons. They are electron-pair donors. Examples are OH-, CN- and NH3 (ammonia has a lone pair of electrons on the nitrogen atom)
Radicals
A radical is a species with an unpaired electron.
The unpaired electron is shown by a dot on the species. As a result of the unpaired electron, radicals are highly reactive. Examples are Cl. and .CH3.
Bond fission
A single covalent bond is a shared pair of electrons between two atoms. Breaking a covalent bond is called bond fission. It can break in two ways:
-Homolytic fission
-Hetrolytic fission
Homolytic fission
In homolytic fission, the bond breaks equally, and each of the bonded atoms receives one of the electrons from the bonded pair. Two radicals are formed.
For example: C2H5Cl → C2H5. + Cl.
The general equation for homolytic fission is:
XY → X. + Y.
Heterolytic fission
In heterolytic fission, the bond breaks unequally with one of the bonded atoms receiving both electrons from the bonded pair. A positively charged ion (cation) and a negatively charged ion (anion) are formed.
For example: CH3CH2Br → CH3CH2+ + :Br-
The general equation for heterolytic fission is:
XY → X+ + Y-
