aliphatic hydrocarbons

Whats a hydrocarbon? Whats it divided into?

• organic compounds of H and C only

• Divided into aliphatic (non aromatic ) and aromatic type

• Aliphatic - straight, branches or non aromatic cyclic structures

Define alkane, alkene, alkynes

Alkane - saturated (single bond C-C ), inert

Alkene - unsaturated, reactive one or more double bonds (c=c)

Alkyne - unsaturated, highly reactive one or more triple bonds (C=-C)

Whats the general formula of alkane and their structure and nomenclature? Draw methane, ethane, propane

• Linear, branched or cyclic

• IUPAC prefix - carbon number and ANE

• general formula CnH2n+2

Physical properties of alkane

• non polar and insoluble in water

• Boiling point increases w/ molecular size

• Common as fuels and solvents

Chemical properties of alkanes

• combustion - burn in oxygen

• Halogenation - halogen added

• Low reactivity

Show complete combustion and incomplete combustion

Show Halogenation (free radical substitution) of chlorine and CH4

Describe low reactivity of alkanes.

• alkanes due to their chemical inertness, hydrophobic nature and low reactivity and occasionally used as inert carriers of excipients in pharmaceutical formulations

Low reactivity - how do alkane solved or carriers work in drug delivery? Eg.

Alkanes such as liquid paraffin (mixture of long chain alkanes) used in:

• oral laxatives

• Topical creams/ ointments (as emollients)

• Suspension vehicles for lipophilic drugs

Petroleum jelly is semisolid mixture of alkanes from c16 to c20 and are used as a base in:

• skin protectants

• Antibacterial ointments

• Cosmetic formulations

General formula and structure and nomenclature of alkenes And draw butene

• Contain at least a C-C double bond

• ENE suffix and indicate position of double bond

• general formula CnH2n

Physical properties of alkenes

• similar to alkanes - but slightly more polar

• Boiling/melting points increase w/ size

• Double bonds affect electron distribution

Chemical properties of alkenes

• electrophilic addition

• Hydrogenation

• Polymerisation

Do electrophilic addition with ethene

Do hydrogenation of ethene

Do polymerisation of ethene

Genera formula and structure and nomenclature of alkynes. Draw ethene and butyne and hexyne

• triple bond - linear geometry

• Named with YNE and specify bond location

• General formula CnH2n-2

What reactions and properties does alkynes have?

• addition reactions similar to alkenes

• Precursor for complex pharmaceuticals

Do addition reactions for propyne

How do alkynes act as precursors in complex pharmaceuticals?

Alkynes serve as versatile scaffold that can be transformed into variety of functional groups:

• hydrogenation —> alkenes or alkanes

• Hydrohalogenation —> vinyl halides

• Hydration —> ketones or aldehydes

• Cycloaddition —> aromatic or heterocyclic systems

These transformations allow alkynes to be foundational in stepwise synthesis of complex pharmaceuticals

How to hydrocarbons have relevance to pharmacy?

• hydrocarbon chains used in local anaesthetic like lidocaine

• Used in ointment, bases , creams and gels

• Drug delivery - enhances membrane permeability

What are the safety and environmental concerns for hydrocarbons?

• volatility —> inhalation risks

• Highly flammable - strict handling needed

• Environmental concerns —> non biodegradability, pollution

Which is an alkene? Ethane, ethene, ethyne

Alkanes are saturated or unsaturated?

Alkyne general formula?

1. Ethene

2. Saturated

3. CnH2n-2