7. Families of Organic Compounds

Question 1

How to name organic compounds

Answer 1

• Rule 1: Determine the longest chain of carbon atoms. This will form the basis of the name.
• Rule 2: Determine which end is nearest to a branch, a double bond or a triple bond. (A double or triple
  bond takes precedence over a branch if they are equidistant from either end of the chain.)
• Rule 3: Number the carbon atoms from the end chosen.
• Rule 4: Name any branches first with the ending -yl (for example, methane becomes methyl and ethane
  becomes ethyl), then the longest chain, and then any single or double bond.
• Rule 5: When two or more branches occur on the same carbon atom, the number of the carbon atom is
  indicated for each branch, with the names given in alphabetical order (ignoring the prefixes described in
  rule 6). Place a comma between numbers and a dash between a number and a word.
• Rule 6: When two or more identical branches occur on the carbon chain, the prefixes di-, tri- and
  tetra- are used.
  TIP: Avoid the following common errors when naming hydrocarbons:
• not identifying the longest chain possible
• not listing the side branches in alphabetical order
• omitting the prefixes di-, tri- and tetra- when they are required.

Question 2

What are halogens?

Answer 2

Halogens (haloalkanes)
Chlorine, fluorine, bromine or iodine that replaces a hydrogen atom
Higher melting and boiling point than their corresponding alkane
Slightly water soluble
Used as flame retardants, aerosol sprays, refrigerant

Halogen atoms are highly electronegative, haloalkanes are polar but only slightly soluble (because the hydrogen bonds between water molecules is stronger than the hydrogen bonds between water and haloalkanes

Alcohol b.p is higher because the OH group is polar which results in stronger attraction than just the dispersion forces in alkanes, alkenea n alkynes
B.p decreases as length of chain increases because the carbon chain part of the molecule is attracted to the carbon chain part of other molecules, as this gets longer it gets stronger
Solubility decreases for the same reason

Question 3

Hydroxy group?

Answer 3

Contains hydroxyl group -OH
Names end in ‘-ol’
CnH2n+1OH
Higher boiling points than corresponding alkanes, alkenes and alkynes
Boiling point decreases as alcohol chain increases
Solubility decreases as alcohol chain increases
Will undergo combustion reactions

Question 4

Carboxyl group?

Answer 4

-COOH is a carboxyl group
Ending is -oic acid
The carbon in the carboxyl group is counted in the longest chain for naming and is always numbered one
Carboxyl group is polar so carboxylic acids will have higher bp than their alkane, alkene and alkyne “likes”
As chain gets longer solubility decreases (same as alcohol)
They are weak acids, they will react with bases to form salt and water, they will react with metals to produce a salt and hydrogen, they weill react with carbonates making a salt, carbon dioxide and water.

Question 5

Esters? (-COO) -oate

Answer 5

Esters are formed from carboxylic acid
A condensation reaction because water is produced
Sulfuric acid is used as a catalyst (helps the reaction to occur)
Name comes from alcohol part then carboxylic acid part with oate ending

Low melting and boiling points because they are non-polar (only dipole-dipole and dispersion forces acting)

Question 6

What is a homologous series?

Answer 6

a series of organic compounds with the same general formula, in which the formula of one molecule different from the next by a -Ch2 group/

Question 7

What is a substitution reaction?

Answer 7

A reaction in which an atom (or group of atoms) is removed and replaced by a different atom (or group of atoms)

Question 8

What is a haloalkane?

Answer 8

A compound with the same structure as an alkane, except that one or more of the hydrogen atoms has been replaced with halogen atoms.

Question 9

What is a functional group?

Answer 9

An atom or group of atoms attached to part of a hydrocarbon chain that influence the physical and chemical properties of the molecule.

Question 10

What is a combustion reaction?

Answer 10

A reaction between a fuel and oxygen (usually) releasing heat energy

Question 11

What is an addition reaction?

Answer 11

A reaction in which one molecule bonds covalently with another molecule without losing any other atoms; only one product is formed.