s3.2 functional groups Flashcards
what is molecular formula?
the actual number of atoms of each element present in a molecule of a compound
what is empirical formula?
the simplest whole number ratio of the elements present in a compound
what is structural formula?
a formula which shows the arrangement of atoms in the molecule of a compound. the formula that shows all the bonding in a molecule is called the full structural formula
what is condensed structural formula?
leaving out the bonds, so butane becomes CH₃CH₂CH₂CH₃
what is skeletal formula?
skeletal formula shows just the carbon skeleton and the functional groups. it is the most basic representation of a molecule
what is a functional group?
a functional group is the atom or group of atoms in a molecule that give it its physical and chemical properties. they are the reactive parts of molecules
what is an R group?
carbon containing groups that are used in the general formulae of organic compounds
what are hydrocarbons?
hydrocarbons are compounds that contain hydrogen and carbon only. they can be further classified as:
1. aliphatic - a hydrocarbon joined together in straight or branched chains
2. alicyclic - a hydrocarbon with carbons joined in a ring structure
3. aromatic (arenes) - a hydrocarbon with at least one benzene ring structure
what’s the difference between saturated and unsaturated hydrocarbons?
saturated hydrocarbons have only single carbon-carbon covalent bonds.
unsaturated carbons have one or more double or triple carbon-carbon covalent bonds.
what is a homologous series?
a homologous series is a family of compounds grouped together based on similarities in their structure and reactivity.
members of a homologous series are similar:
- they have the same functional group
- they have the same general formula
- they differ from successive members by a unit of CH₂
- they have similar chemical properties
- they have similar physical properties that show a gradation
what are alkanes?
functional group: alkyl
general formula: CₙH₂ₙ₊₂
saturated hydrocarbon
types of reaction: combustion, free radical substitution
what are alkenes?
functional group: alkenyl
general formula: CₙH₂ₙ
unsaturated hydrocarbon (contains at least one double bond)
types of reaction: combustion, electrophilic addition, reduction with hydrogen
what are alkynes?
functional group: alkynyl
general formula: CₙH₂ₙ₋₂
unsaturated hydrocarbon (contains at least one triple bond)
types of reaction: combustion, electrophilic addition
what are aldehydes?
functional group: aldehyde
general formula: CₙH₂ₙO, R-CHO
types of reaction: oxidation, reduction
carbonyl compound - the carbonyl group is located in terminal position (at one end of the molecule)
what are ketones?
functional group: ketone
general formula: CₙH₂ₙO, R-CO-R’
types of reaction: reduction
carbonyl compound: the carbonyl group is attached to a carbon atom within the carbon chain
what are esters?
functional group: ester
general formula: CₙH₂ₙO₂, R-COO-R’
type of reaction: nucleophilic substitution reactions between alcohols and carboxylic acids
-> asymmetric, carbonyl functional group, used as artificial flavorings and in perfumes
what are ethers?
function group: ether
general formula: CₙH₂ₙO₂₊₂, R-O-R’
-> have an alkoxy functional group that is composed of an oxygen atom bonded to two alkyl groups. like the esters, ethers are also used in food flavourings and as fragances in perumes.
what are alcohols?
functional group: hydroxyl
general formula: CₙH₂ₙ₊₁OH, R-OH
type of reaction: combustion, oxidation, nucleophilic substitution
-> alcohols are described as primary, secondary or tertiary depending on the number of carbon atoms attached to the carbon with the -OH group
what are carboxylic acids?
functional group: carboxyl
general formula: CₙH₂ₙO₂, R-COOH
type of reaction: nucleophilic substitution, reduction
what are nitriles?
functional group: nitrile
general formula: CₙH₂ₙ₋₁N
what are amines?
functional group: amine/amino
general formula: CₙH₂ₙ₊₃N, R-NH₂
type of reaction: can act as bronsted-lowry bases and lewis bases
->amines are also classified as primary, secondary or tertiary. primary amines contain -NH₂, secondary amines contain -NHR₂, tertiary amines contain -NR₃
what are amides?
functional group: carboxamide amido
general formula: R-CONRR’
what are arenes?
functional group: phenyl
general formula: R-C₆H₅
what are halogenoalkanes?
functional group: fluro-, chloro, bromo-, iodo-
general formula: CₙH₂ₙ₊₁X
type of reaction: nucleophilic substitution
-> halogenoalkanes are also described as primary, secondary or tertiary depending on the number of carbon atoms attached to carbon atom of the C-X
what are the physical trends of homologous series?
for a given homologous series, physical properties such as melting and boiling points change gradually with each successive member. this is because the length of the carbon chain increases by CH₂ each time, altering the intermolecular forces and therefore the physical properties.
boiling point and melting point increase with:
- increasing molar mass
- increase in carbon atoms
- increase in carbon chain length
- stronger london forces
