topic 10/20 Flashcards
define a homologous series
a series of compounds of the same family, with the same general formula, which differ from each other by a common structural unit (CH2, methylene group)
explain the trend in boiling points and density of members of homologous series
boiling point/density increases as length of carbon chain increases:
- molecular mass increases/no of C atoms increases
- London forces increase as the molecules get bigger
describe and explain the trend in solubility of members of a homologous series
less soluble as homologous series is ascended:
hydrocarbon chain is non-polar (hydrophobic) and as no of carbons increase, this increases the percentage of the molecule that is unattractive to water.
what does the solubility of a compound in water depend on?
solubility in water depends on the ability of the water molecules to attract dipoles in the organic compound.
describe physical and chemical properties of homologous series
- physical properties change gradually as the length of the carbon chain increases
- similar chemical properties
general formula of alkanes
CnH2n+2
general formula for alkenes
CnH2n
general formula for alkynes
CnH2n-2
general formula for ketones
CnH2nO
general formula for alcohols
CnH2n+1OH
general formula for aldehydes
CnH2n+2
general formula for carboxylic acids
CnH2n+1COOH
define an empirical formula
the simplest ratio of the atoms within a molecule of the compound
define the molecular formula
shows the actual number of atoms of each type in the molecule
define the structural formula
shows the actual arrangement of the atoms in a molecule by drawing the bonds as lines between letters representing the atoms
define a skeletal formula
each carbon is represented by an angle, or termination in a line and the hydrogen atoms are just assumed
state the two ways that structural formulae can be represented.
- full format
- condensed format
describe alkanes as a class of organic compounds
saturated hydrocarbons
describe alkenes as a class of organic compounds
unsaturated hydrocarbons- carbon and hydrogen atoms with one or more carbon-carbon double bond in their chemical structure
describe alkynes as a class of organic compounds
organic molecules made of the functional group carbon-carbon triple bonds
describe halogenoalkanes as a class of organic compounds
organic compounds that contain one or more halogen atom (chlorine, bromine, fluorine, or iodine) attached to a carbon atom in an alkane molecule
- RX, where R=alkyl group, H= halogen
describe alcohols as a class of organic compounds
one or more hydroxyl (―OH) groups attached to a carbon atom of an alkyl group (hydrocarbon chain).
describe ethers as a class of organic compounds
characterized by an oxygen atom bonded to two alkyl or aryl groups
R−O−R′
describe aldehydes as a class of organic compounds
a carbon atom shares a double bond with an oxygen atom, a single bond with a hydrogen atom, and a single bond with another atom or group of atoms
R−CH=O
describe ketones as a class of organic compounds
R−C(=O)−R’
describe esters as a class of organic compounds
any of a class of organic compounds that react with water to produce alcohols and organic or inorganic acids
R-C(=O)-O
describe carboxylic acids as a class of organic compounds
any of a class of organic compounds in which a carbon atom is double bonded to an oxygen atom and to a hydroxyl group (―OH) by a single bond
R−COOH
describe amines as a class of organic compounds
organic compounds that contain nitrogen atoms with a lone pair
R-CO- NH2
describe amides as a class of organic compounds
R(CO)NR2
describe nitriles as a class of organic compounds
any of a class of organic compounds having molecular structures in which a cyano group (―C ≡ N) is attached to a carbon atom (C)
R-C[triple]N
describe arenas as a class of organic compounds
aromatic hydrocarbons- implies a particular sort of delocalized bonding
CnH2n−6
define functional groups
a group of atoms that determines a molecule’s reactivity
describe phenyl as a functional group
a benzene ring, minus a hydrogen
describe hydroxyl as a functional group
- OH
describe carbonyl as a functional group
[C=O]
describe carboxyl as a functional group
−COOH
Describe a carboxamide as a functional group
-CO-NH2
Describe aldehydes as a functional group
−CH=O
Esters as a functional group
-COO-
Ethers as a functional group
R−O−R
Amines as a functional group
-NH2
Nitrile as a functional group
−C≡N
Alkyl functional group
−C≡N
Alkyl as a functional group
formed by removing a hydrogen atom from the molecule of alkane.
Alkenyl group
Hydrocarbon group formed when a hydrogen atom is removed from an alkene group
Alkynyl group
Obtained by the removal of one hydrogen atom that is linked to a triply bonded carbon atom
Define structural isomers
Compounds with the same molecular formula but different arrangement of atoms
Define stereoisomers
Have the same structural formula but differ in their spatial arrangement
Describe the different types of stereoisomerism
- Stereoisomerism:
Configurations isomerism (cis/trans E/Z, optical isomerism), conformational isomerism - Structural isomerism:
Positional isomers, functional group isomers, chain isomerism
Describe the difference between conformational isomers and configurational isomers
Conformational: can interconvert by rotation about a sigma bond
Configurational: can only interconvert by breaking and reforming a bond
why do alkanes only undergo free radical substitution?
they have a low reactivity due to the:
- strength of the C-C and C-H bonds
- lack of polarity
incomplete combustion of alkanes
C, CO, H2O
complete combustion of alkanes
CO2, H2O
combustion of alkanes is …
highly exothermic
describe heterolytic fission
results in the formation of a positive and negative ion
describe homolytic fission
results in the formation of two radicals
what condition is necessary for free radical substitution?
UV light
define free radical substitution
a type of substitution reaction where a radical replaces a different atom or group of atoms
what bonds can UV light break/not break?
it can break bonds between halogens but not between C-H bonds (too strong)
why would excess methane be needed in free radical substitution?
to reduce further substitution
describe the free radical substitution mechanism
check notes
give 3 limitations of free radical substitutions
- any of the hydrogens can be substituted so a number of products can be formed
- multi-substitutions may occur
- it is not effective to create a specific halogenoalkane
