Properties of Hydrocarbons
Amides — Properties
- 1° amides have 2 N-H bonds so form stronger bonds than the carboxylic acids → higher boiling points
- Soluble in water (solubility decreases as #C increases)
- 2° amides also experience hydrogen bonding but 3° amides do not
- NH bonds are polar → properties are similar to those of carboxylic acids
- Weak bases
- Many are solid at room temperature
Esters — Properties
- Polar
- No hydroxyl group (OH) so don't form hydrogen bonds with each other but can with water → lower
boiling points
- Reactive liquids
- Not acidic
- Used in industry
- Small, nice smell
- Responsible for many odors of fruits and flowers
- Formed when a carboxylic acid reacts with an alcohol
Carboxylic Acids — Properties
- Carboxylic acids form strong hydrogen bonds between each other and with water
- Very polar due to OH and C=O bonds
- Higher boiling points than alcohols
- Smaller acids are water soluble due to hydrogen bonding but solubility decreases as #C increases
- Weak acids — the hydrogen on the carboxyl group dissociates easily (OH doesn't act like OH⁻)
- Strong odors
- React with alcohols to form organic salts called esters
- If there are more than 2 carboxyl groups, they may be named as branches (e.g. tricarboxylic acids)
Amines — Properties
- Polar due to C-N and N-H bonds
- Found in many biological molecules i.e. amino acids
- Higher boiling points than alkanes due to N-H family
- H-bonds (only 1° and 2° amines; 3° amides do not)
- 3° amines cannot form H-bonds so have lower boiling points than 1° or 2° amines
- Smaller amines are water soluble (solubility decreases as # of C increases)
- N-H is less polar than OH → hydrogen bonding is weaker than in alcohols → amines have lower boiling
points than alcohols
- Like ammonia, amines are weak bases
- Toxic
- Unpleasant odors of decay and decomposition are caused by amines
e.g. cadaverine contributes to odor of decaying flesh
- Fishy smell of seafood caused by amines (use vinegar or lemon juice to neutralize the smell)
, Properties of Hydrocarbons
Aldehydes — Properties
- Boiling points are lower than the alcohols (no OH group) middle, but higher than alkanes (more polar
due to carbonyl group C=O which is very polar)
- No hydrogen bonds between aldehydes but can form them with water
- Small aldehydes are water soluble (solubility decreases as C increases)
- Sharp pungent odors that become more fragrant as size increases
- Common flavourings like vanillin, oil of cinnamon, oil of almonds
- Carbonyl group is polar due to oxygen → aldehydes are very polar (can act as polar solvents)
- Also can be non-polar solvents due to the non-polar hydrocarbon portion
Ketones — Properties
- Polar due to carbonyl group → polar solvents
- Also non-polar due to hydrocarbon part
- Less reactive than the aldehydes
- Lower boiling points than alcohols but higher than alkanes
- No OH group so no hydrogen bonding between them but can with water
- Water soluble (solubility decreases as C increases)
- Smell sweet (used in perfumes)
- Also have many industrial uses
Ethers — Properties
- No hydrogen bonding between ethers (no OH)
- Water soluble (solubility decreases as # of C increases)
- React very slowly with air to form peroxides that can be highly explosive
- BPs less than alcohols — they are less polar (and can't form H-bonds with each other)
- Flammable
- Generally unreactive
- Very polar (C-O) and are able to dissolve in non-polar solvents (alkyl group)
- Higher boiling points than alkanes due to polarity of oxygen (strong intermolecular bonds)
Alcohols — Properties
- Very polar due to the OH group, therefore very reactive
- Higher boiling points than alkanes with the same number of carbons due to hydrogen bonding
- Small alcohols (less than 5 C3) are soluble in polar solvents (solubility decreases as # of C3 increases)
- In longer alcohols, the hydrocarbon portion is non-polar so soluble in non-polar solvents
- Most alcohols are liquid at room temperature
- Extremely flammable
- Most are poisonous
- The high boiling points of alcohols are explained by the increased forces of attraction between
molecules due to hydrogen bonding (same reason boiling point of water is much higher than expected —
both contain the hydroxyl group OH)
- In methanol, the O-H bond is quite polar due to oxygen having much higher electronegativity than
hydrogen → hydrogen atom carries slight positive charge and oxygen atom slight negative charge →
electrostatic attraction between oxygen of one molecule and hydrogen of another →
Amides — Properties
- 1° amides have 2 N-H bonds so form stronger bonds than the carboxylic acids → higher boiling points
- Soluble in water (solubility decreases as #C increases)
- 2° amides also experience hydrogen bonding but 3° amides do not
- NH bonds are polar → properties are similar to those of carboxylic acids
- Weak bases
- Many are solid at room temperature
Esters — Properties
- Polar
- No hydroxyl group (OH) so don't form hydrogen bonds with each other but can with water → lower
boiling points
- Reactive liquids
- Not acidic
- Used in industry
- Small, nice smell
- Responsible for many odors of fruits and flowers
- Formed when a carboxylic acid reacts with an alcohol
Carboxylic Acids — Properties
- Carboxylic acids form strong hydrogen bonds between each other and with water
- Very polar due to OH and C=O bonds
- Higher boiling points than alcohols
- Smaller acids are water soluble due to hydrogen bonding but solubility decreases as #C increases
- Weak acids — the hydrogen on the carboxyl group dissociates easily (OH doesn't act like OH⁻)
- Strong odors
- React with alcohols to form organic salts called esters
- If there are more than 2 carboxyl groups, they may be named as branches (e.g. tricarboxylic acids)
Amines — Properties
- Polar due to C-N and N-H bonds
- Found in many biological molecules i.e. amino acids
- Higher boiling points than alkanes due to N-H family
- H-bonds (only 1° and 2° amines; 3° amides do not)
- 3° amines cannot form H-bonds so have lower boiling points than 1° or 2° amines
- Smaller amines are water soluble (solubility decreases as # of C increases)
- N-H is less polar than OH → hydrogen bonding is weaker than in alcohols → amines have lower boiling
points than alcohols
- Like ammonia, amines are weak bases
- Toxic
- Unpleasant odors of decay and decomposition are caused by amines
e.g. cadaverine contributes to odor of decaying flesh
- Fishy smell of seafood caused by amines (use vinegar or lemon juice to neutralize the smell)
, Properties of Hydrocarbons
Aldehydes — Properties
- Boiling points are lower than the alcohols (no OH group) middle, but higher than alkanes (more polar
due to carbonyl group C=O which is very polar)
- No hydrogen bonds between aldehydes but can form them with water
- Small aldehydes are water soluble (solubility decreases as C increases)
- Sharp pungent odors that become more fragrant as size increases
- Common flavourings like vanillin, oil of cinnamon, oil of almonds
- Carbonyl group is polar due to oxygen → aldehydes are very polar (can act as polar solvents)
- Also can be non-polar solvents due to the non-polar hydrocarbon portion
Ketones — Properties
- Polar due to carbonyl group → polar solvents
- Also non-polar due to hydrocarbon part
- Less reactive than the aldehydes
- Lower boiling points than alcohols but higher than alkanes
- No OH group so no hydrogen bonding between them but can with water
- Water soluble (solubility decreases as C increases)
- Smell sweet (used in perfumes)
- Also have many industrial uses
Ethers — Properties
- No hydrogen bonding between ethers (no OH)
- Water soluble (solubility decreases as # of C increases)
- React very slowly with air to form peroxides that can be highly explosive
- BPs less than alcohols — they are less polar (and can't form H-bonds with each other)
- Flammable
- Generally unreactive
- Very polar (C-O) and are able to dissolve in non-polar solvents (alkyl group)
- Higher boiling points than alkanes due to polarity of oxygen (strong intermolecular bonds)
Alcohols — Properties
- Very polar due to the OH group, therefore very reactive
- Higher boiling points than alkanes with the same number of carbons due to hydrogen bonding
- Small alcohols (less than 5 C3) are soluble in polar solvents (solubility decreases as # of C3 increases)
- In longer alcohols, the hydrocarbon portion is non-polar so soluble in non-polar solvents
- Most alcohols are liquid at room temperature
- Extremely flammable
- Most are poisonous
- The high boiling points of alcohols are explained by the increased forces of attraction between
molecules due to hydrogen bonding (same reason boiling point of water is much higher than expected —
both contain the hydroxyl group OH)
- In methanol, the O-H bond is quite polar due to oxygen having much higher electronegativity than
hydrogen → hydrogen atom carries slight positive charge and oxygen atom slight negative charge →
electrostatic attraction between oxygen of one molecule and hydrogen of another →
