s3.2 functional groups

Question 1

what is molecular formula?

Answer 1

the actual number of atoms of each element present in a molecule of a compound

Question 2

what is empirical formula?

Answer 2

the simplest whole number ratio of the elements present in a compound

Question 3

what is structural formula?

Answer 3

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

Question 4

what is condensed structural formula?

Answer 4

leaving out the bonds, so butane becomes CH₃CH₂CH₂CH₃

Question 5

what is skeletal formula?

Answer 5

skeletal formula shows just the carbon skeleton and the functional groups. it is the most basic representation of a molecule

Question 6

what is a functional group?

Answer 6

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

Question 7

what is an R group?

Answer 7

carbon containing groups that are used in the general formulae of organic compounds

Question 8

what are hydrocarbons?

Answer 8

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

Question 9

what’s the difference between saturated and unsaturated hydrocarbons?

Answer 9

saturated hydrocarbons have only single carbon-carbon covalent bonds.
unsaturated carbons have one or more double or triple carbon-carbon covalent bonds.

Question 10

what is a homologous series?

Answer 10

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

Question 11

what are alkanes?

Answer 11

functional group: alkyl
general formula: CₙH₂ₙ₊₂
saturated hydrocarbon
types of reaction: combustion, free radical substitution

Question 12

what are alkenes?

Answer 12

functional group: alkenyl
general formula: CₙH₂ₙ
unsaturated hydrocarbon (contains at least one double bond)
types of reaction: combustion, electrophilic addition, reduction with hydrogen

Question 13

what are alkynes?

Answer 13

functional group: alkynyl
general formula: CₙH₂ₙ₋₂
unsaturated hydrocarbon (contains at least one triple bond)
types of reaction: combustion, electrophilic addition

Question 14

what are aldehydes?

Answer 14

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)

Question 15

what are ketones?

Answer 15

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

Question 16

what are esters?

Answer 16

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

Question 17

what are ethers?

Answer 17

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.

Question 18

what are alcohols?

Answer 18

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

Question 19

what are carboxylic acids?

Answer 19

functional group: carboxyl
general formula: CₙH₂ₙO₂, R-COOH
type of reaction: nucleophilic substitution, reduction

Question 20

what are nitriles?

Answer 20

functional group: nitrile
general formula: CₙH₂ₙ₋₁N

Question 21

what are amines?

Answer 21

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

Question 22

what are amides?

Answer 22

functional group: carboxamide amido
general formula: R-CONH₂

Question 23

what are arenes?

Answer 23

functional group: phenyl
general formula: R-C₆H₅

Question 24

what are halogenoalkanes?

Answer 24

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

Question 25

what are the physical trends of homologous series?

Answer 25

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