Introduction to organic chemistry Flashcards
Classification of organic compounds/hydrocarbons (3)
- Aliphatic → open chains
- Acyclic → closed ring
- Aromatic → contain benzene ring
Functional group
Atom/group of atoms within the organic compound that is responsible for its characteristic chemical properties
Homologous series
- Family of compounds having the same functional group
- Represented by general formula
- Differs from successive member by -CH₂- group (methylene)
- Similar chemical properties
Classes of compounds (6)
- Hydrocarbons
- Halogen derivatives
- Hydroxyl compounds
- Carbonyl compounds
- Carboxylic acids and derivatives
- Nitrogen compounds
Hydrocarbons (3)
- Alkanes → saturated
- Alkene → double bond
- Alkyne → triple bond
Halogen derivatives (2)
- Halogenoalkane → e.g. chloroethane
2. Halogenoarene → benzene ring → e.g. chlorobenzene
Hydroxyl compounds (2)
- Alcohol → e.g. ethanol
2. Phenol → benzene ring
Carbonyl compounds (2)
C=O
- Aldehyde → at the end → e.g. ethanal
- Ketone → in the middle → e.g. propanone
Carboxylic acids and derivatives (3)
- Carboxylic acid → COOH → e.g. ethanoic acid
- Ester → e.g. methyl ethanoate
- Acyl halide/acid halide → COX → e.g. propanoyl chloride
Nitrogen compounds
- Amine → NH₂ → e.g. ethylamine
- Amide → CONH₂ → e.g. propanamide
- Amino acid → H₂NCHRCOOH
- Nitrile → C≡N → e.g. propanenitrile
Formulae of Organic Compounds (3)
- Empirical formula → simplest ratio
- Molecular formula → actual number
- Structural formula
Structural formula (4)
- Condensed → sequential arrangement (CH₃CH₃)
- Displayed/full → bonds between atoms except rings
- Stereochemical → spatial structure
- Skeletal → no show C and H
IUPAC Nomenclature
- Prefix(es) → side groups → alphabetical order
- Root → longest continuous carbon chain
- Suffix → principal functional group
Root
- meth-
- eth-
- prop-
- but-
- pent-
- hex-
- hept-
- oct-
- non-
- dec-
Suffix
- Carboxylic acid → -oic acid
- Ester → -yl … oate
- Acyl halide → -oyl halide
- Amide → -amide
- Nitrile → -nitrile
- Aldehyde → -al
- Ketone → -one
- Alcohol → -ol
- Amine → -amine
Prefix
Screw this
Mechanisms
- Organic reactions involve breaking and forming of covalent bonds
- Illustrate flow of e⁻ density from e⁻-rich to e⁻-deficient sites
Types of bond fission/cleavage (breaking) (2)
- Homolytic fission
2. Heterolytic fission
Homolytic fission
- 1 e⁻ goes to each atom
- Forms free radicals
Heterolytic fission
- Both e⁻ go to same atom
- Forms + and - ions
- Both go to leaving group → when C less electronegative than X → carbocation
- Both go to carbon → when C more electronegative than X → carbanion
Degree of substitution
- Number of alkyl or aryl groups bonded to it
- Primary, secondary, tertiary, quaternary
Types of organic species (attacking) (3)
- Electrophile
- Nucleophile
- Free radical
Electrophile
- e⁻ pair acceptor (subset of Lewis acids)
- e⁻-deficient
- Attracted to regions of negative charge/e⁻-rich sites in a molecule
- May possess empty low-lying orbitals
Nucleophile
- e⁻ pair donor (subset of Lewis base)
- e⁻-rich
- Attracted to regions of negative charge/e⁻-deficient sites in a molecule
- Possess at least 1 lone pair of e⁻
Free radical
- Contains unpaired e⁻ formed from homolytic fission
- Electrically neutral
Types of organic reactions
- Addition → when there is unsaturation
- Substitution
- Elimination → removal from adjacent Cs → multiple bonds
- Hydrolysis
- Condensation
- Oxidation
- Reduction
- Rearrangement
Isomerism
Existence of ≥ 2 compounds with the same molecular formula but with different arrangement of the atoms
Types of isomerism (2)
- Constitutional isomerism
2. Stereoisomerism
Constitutional isomerism
Same molecular formula but different structural formula
Types of constitutional isomerism (3)
- Chain isomers → straight vs branched
- Positional isomers → diff position of functional group
- Functional group isomers → diff functional groups
Stereoisomerism
Same molecular formula but different spatial arrangement of atoms
Types of stereoisomerism (2)
- Cis-trans isomerism
2. Enantiomerism
Cis-trans isomerism
- Restricted rotation about a double bond or a bond in a ring structure
- Double bond with two different groups attached to each of the two atoms in the double bond or a ring structure with two different groups attached to two atoms in the ring structure
- Maximum number of isomers = 2^n where n is no. of C=C bonds
Cis
Same side
Trans
Opposite sides
Properties of cis-trans isomers
- Generally have similar chemical properties
- Different physical properties (could be because of polarity/fitting into a crystalline lattice)
Enantiomerism
If it forms a non-superimposable mirror image → chiral compounds
Chiral compounds
- Do not have a plane of symmetry
- Usually contains one or more chiral centres
Chiral carbon
- sp³ hybridised
- 4 different groups attached to it
Rotation of plane-polarised light and optical activity
Enantiomers rotate plane-polarised light in different directions (clockwise/anti-clockwise) → optically active
Plane-polarised light
Light-wave vibrates along same plane
Racemic mixture
Equal proportion of enantiomers → not optically active
Molecules with > 1 chiral centres
Generally, a molecule with n chiral centers → maximum of 2^n stereoisomers
Diastereomers
Stereoisomers which are not mirror images of each other
Meso compound
> 1 chiral centre but has a plane of symmetry → mirror images that are superimposable → optically inactive
