Question

write the structural formula of alkane, alkene and alkynes​

Answer 1

Alkanes, alkenes and alkynes are simple hydrocarbon chains with no functional groups. Alkanes are identified because the carbon chain has only single bonds. Common alkanes include methane (natural gas), propane (heating and cooking fuel), butane (lighter fluid) and octane (automobile fuel). Alkenes have at least one double bond and alkynes have at least one triple bond. The most common alkyne is ethyne, better known as acetylene. The generic formula for alkanes is CnH2n+2, where n is the number identified by the prefix. Alkenes have the formula CnH2n and alkynes use the formula CnH2n-2.

Writing the formulas for simple alkanes, alkenes and alkynes is as simple as determining how many carbons are in the formula and then putting that number into the generic formula for that hydrocarbon. Since alkanes do not have any real parts to identify, unlike all other organic molecules, there is no need to number the carbons.

propane octane 2-pentene 4-decyne

prop = 3 oct = 8 pent = 5 dec = 10

C3H2(3)+2 C8H2(8)+2 C5H2(5) C10H2(10)-2

C3H8 C8H18 C5H10 C10H18

Naming the alkanes, alkenes and alkynes is the opposite of the formula writing process. To determine which type of molecule you are working with you should compare the carbons to the hydrogens.

CH4 C6H10 C2H6 C7H14

C:H = 1:2(1)+2 C:H = 6:2(6)-2 C:H = 2:2(2)+2 C:H = 7:2(7)

alkane alkyne alkane alkene

1C = meth 6C = hex 2C = eth 7C = hept

methane hexyne ethane heptene

To determine the position of the double or triple bond would require seeing a Lewis Dot Diagram.

Answer 2

The structural formula are as follows

for alkane  -  CₙH₂ₙ₊₂

for alkene  - CₙH₂ₙ

for alkyne  - CₙH₂ₙ₋₂

1. FOR ALKANES -  Alkanes are called as hydrocarbons because there is no double bond between them hence there is a single bond .They are generally used in the process of combustion . An example of alkane can be methane i.e. CH₄
2. FOR ALKENES - Alkenes are called as unsaturated hydrocarbons as there is a double bond between the carbons . They also undergoes combustion reaction but also goes addition reaction . They undergo self-addition to form large structures called polymers . An example is ethene C₂H₄
3. ALKYNES - Alkynes are also called as unsaturated hydrocarbons as there is a triple bond formed between the carbon atoms . They also undergoes combustion and addition reactions . An example is C₂H₂ (acetylene )

Answer 3

The structural formula are as follows

for alkane  -  CₙH₂ₙ₊₂

for alkene  - CₙH₂ₙ

for alkyne  - CₙH₂ₙ₋₂

1. FOR ALKANES -  Alkanes are called as hydrocarbons because there is no double bond between them hence there is a single bond .They are generally used in the process of combustion . An example of alkane can be methane i.e. CH₄
2. FOR ALKENES - Alkenes are called as unsaturated hydrocarbons as there is a double bond between the carbons . They also undergoes combustion reaction but also goes addition reaction . They undergo self-addition to form large structures called polymers . An example is ethene C₂H₄
3. ALKYNES - Alkynes are also called as unsaturated hydrocarbons as there is a triple bond formed between the carbon atoms . They also undergoes combustion and addition reactions . An example is C₂H₂ (acetylene )