organic Flashcards
hydrocarbon
organic compound that contains only carbon & hydrogen
saturated molecule
molecule that contains only C-C bonds
(substitution reactions)
unsaturated molecule
molecule that contains C=C or C≡C bonds
(addition reactions)
structural isomerism
molecules with identical molecular formulae, but different atomic structures
i.e. chain & positional isomers
geometric isomerism (stereoisomerism)
molecules with identical molecular formulae, but different spatial arrangements of atoms
i.e. when both carbons in a C=C bond (alkene) are attached to two different groups
cis-isomer : vertical symmetry
trans-isomer : vertical asymmetry
relationship between mass & dispersion forces
↑mass = ↑electrons = ↑dispersion forces
relationship between carbon chain length & dispersion forces
↑length = ↑surface area = ↑dispersion forces
even-numbered vs odd-numbered carbon chains
even-numbered carbon chains pack more tightly than odd-numbered carbon chains
∴ stronger dispersion forces
∴ greater boiling/melting point
straight vs branched carbon chains
straight carbon chains pack more tightly than branched carbon chains
∴ stronger dispersion forces
∴ greater boiling/melting point
markovnikov’s rule
when alkenes undergo addition reactions with H₂O or hydrogen halides, hydrogen joins the carbon of the C=C bond with more hydrogen (major product)
small proportion of products may oppose this rule (minor product)
primary, secondary & tertiary alcohols
primary : OH attached to a carbon with at least two hydrogen
secondary : OH attached to a carbon with one hydrogen
tertiary : OH attached to a carbon with no hydrogen
relationship between carbon chain length & hydrogen bonding
↑length = ↓hydrogen bonding attraction
∵ ↑overall non-polar nature
relationship between alcohol type & physical properties
boiling point : primary > secondary > tertiary
solubility : tertiary > secondary > primary
∵ branching - OH becomes less accessible to form hydrogen bonds
relationship between chain length & alcohol solubility
↑length = ↓solubility
∵ non-polar hydrocarbon chain becomes stronger
why are carboxylic acids more acidic than alcohols ?
hydrogen atom is more exposed
∴ greater ability to donate a proton (↑Kₐ )
intermolecular forces of carboxylic acids
two molecules of carboxylic acid can form a dimer connected by two hydrogen bonds
∴ stronger hydrogen bonding
∴ stronger dispersion forces (doubled mass)
why are carboxylic acids more soluble than alcohols ?
COOH is more hydrophilic than OH
∵ both CO & OH can hydrogen bond with H₂O
intermolecular forces of haloalkanes
dispersion forces & dipole-dipole attractions
∵ C-halogen bonds have high differences in electronegativity
aldehydes
C=O in a terminal position
ketones
C=O in a non-terminal position
intermolecular forces of aldehydes & ketones
dispersion forces & dipole-dipole attractions
∵ ↑electronegative oxygen (polar C=O bond)
intermolecular forces of esters (COO)
dispersion forces & dipole-dipole attractions
esters can accept hydrogen bonds from H₂O, but itself cannot hydrogen bond with H₂O
∵ no hydrogen atom
∴ slightly soluble from polarity, but less soluble than carboxylic acids
basicity of amines
amines accept H⁺ if reacted in solution (brønsted-lowry base)
e.g. ethylamine + H⁺ → ethylammonium ion
intermolecular forces of amines
dispersion forces & hydrogen bonding
highly polar amino group capable of forming multiple hydrogen bonds
∴ high boiling point
∴ high solubility
functional group priorities
carboxyl > ester > amide > nitrile > carbonyl (aldehyde) > carbonyl (ketone) > hydroxyl > amino > alkene > alkyne > halo
alkane reactivity
unreactive
∵ strong sigma bond
substitution reactions with halogens (UV) to form haloalkanes
combustion reactions with O₂ to produce CO₂, H₂O & heat
alkene reactivity
↑reactivity than alkanes
∵ weak pi bond
reduction reactions with H₂ (Ni/heat) to form alkanes
addition reactions with H₂O (H₃PO₄/heat) to form alcohols
addition reactions with halogens (e.g. Br₂) to form dihaloalkanes
addition reactions with hydrogen halides (e.g. HBr) to form haloalkanes
addition polymerization
monomers undergo addition reactions (catalyst/heat) to form polymers
e.g. ethene → polyethene
combustion of alcohols
alcohol + O₂ → CO₂ + H₂O + energy
oxidation of alcohols
oxidation reactions with K₂Cr₂O₇/KMnO₄ (H⁺/heat) to form :
primary : aldehyde
secondary : ketone
tertiary : inert (no replaceable hydrogen)
esterification of alcohols
alcohol + carboxylic acid → ester + H₂O
(H₂SO₄)
e. g. methanol + propanoic acid → methyl propanoate + H₂O
- - -
hydrolysis : opposite of condensation
ester + H₂O → alcohol + carboxylic acid
(dilute H₂SO₄/heat)
haloalkane reactivity
elimination reactions with NaOH (heat) to form alkenes
substitution reactions with NaOH to form alcohols
substitution reactions with KCN (ethanol/heat) to form nitriles (C≡N)
substitution reactions with NH₃ to form amines (NH₂)
substitution reactions with halogens to form dihaloalkanes
aldehyde & ketone reactivity
aldehyde :
oxidation reactions with K₂Cr₂O₇/KMnO₄ (H⁺/heat) to form carboxylic acids
∵ terminal C=O (replaceable hydrogen)
ketones cannot oxidize
∵ non-terminal C=O (no replaceable hydrogen)
nitrile reactivity
reduction reactions with H₂ (Ni/heat) to form amines (NH₂)
e.g. ethanenitrile + H₂ → ethanamine
amine reactivity
condensation reactions with carboxylic acids to form amides (CONH₂)
e.g. methanamine + ethanoic acid → methylethanamide + H₂O
bromine water test
alkene : brown → colorless
alkane : brown → brown
acidified potassium dichromate test
1° & 2° alcohol : orange → green
3° alcohol : orange → orange
acidified potassium permanganate
1° & 2° alcohol : purple → colorless
3° alcohol : purple → purple
