Organic Chemistry Part 2

Hi guys, you're welcome to mystudyrom my name is David.

Hope the first part helped you a lot and if you are not getting it or feel confused you can use the comment box below…thanks

Today we will be moving to the next part in the organic chemistry so feel relaxed and let's ride on….

Now let's continue from where we stopped in our chemistry…I guess we are going into the alkene family today..

But before we go into that let's see some chemical properties of the alkane family.

As we've discussed in the previous part we said that the alkane family undergo substitution reaction so let's check it out 

Ethane + chlorine

C₂H₆ + Cl₂ --------->  C₂H₅Cl  + HCl

Ethane + Bromine

C₂H₆ + Br₂ --------->  C₂H₅Br +  HBr

Alkane + Fluorine=

I hope you can do for fluorine…just give it a try it’s not that hard.

Another reaction alkanes undergo is combustion reaction.

So let's use ethane ad example

C₂H₆ + O₂   ------>  CO  +  H₂O

Also butane

C₄H₁₀   ------>     CO   +  H₂O

I guess you're wondering why we got CO (carbon(iv)oxide) and water as our products right?

Not to worry the magic is that in the combustion of hydrocarbons the products we have are carbon dioxide and water only.

So let's go into today's topic the unsaturated hydrocarbons which are the alkene and the alkyne family.

So let's start with the alkene family:

The alkene family are unsaturated hydrocarbons with double bond attached to one of the carbons present in the compound.

The alkene family has a general formula of CnH2n.

So now let's check out the list of compounds present in the alkene family.

Starting with Ethene the first of the family.

I guess you will be asking why is it ethene not methene?  

    Don't worry I will explain it now.

The alkene starts with ethene because if we use their general formula which is CnH2n we won't get a compound that obey the tetravalency of carbon

Using their general formula CnH_2n

Where n=1

C₁H_2*1

C₁H₂

And that is CH₂

and if we try to manipulate by attaching the four bonds to carbon by sharing them to the hydrigen two-two then one of the rule is broken and the rule is that "only one bond propene

attached to hydrogen" because hydrogen needs only one bond to make it duplet.

What do I mean by all these stories?

Hydrogen only need to be attached to an element to form a duplet structure since it has only one electrons in its shell.

So let's continue from where I branched to explain why methene is not present.

So now the first compound ethene

Using their general formula C_nH_2n

Where n=2

C₂H_2*2

C₂H₄

Ethene

Another example is propene

Using their general formula CnH2n

Prop C=3 (three carbons is prop)

Where n=3

Then C₃H_3*2

C₃H₆

propene

 

Guys i hope you can solve for the rest using that same method because that's the easiest method you can use.

So let's check out the characteristics of the alkene family.

    Characteristics of the alkene Family

• They are unsaturated hydrocarbons

• They consists of double bonds attached to their chains

•   They undergo addition reaction because of the incomplete number of hydrogen bond attached to the carbons.

So now let's see how we can prepare alkenes

Preparation of alkenes

• Dehydration of alcohols using conc.acid e.g H₂SO₄

C₂H₅OH + H₂SO₄ ----------------> C₂H₄  +  H₂O

ethanol                           ethene     water

• The dehydrohalogenation of alkyl halides

  as the dehydrohalogenation implies it means the removal of both hydrogen and halogen from an organic compound.

Using chloroethane

   C₂H₅Cl --------------> C₂H₄ + HCl

 • The  dehalogenation of alkanes.

As the word dehalogenation implies it means the removal of halogen from an organic compound.

Using Chloroethane with sodium as catalyst

C₂H₄Cl₂ + 2Na ---------> C₂H₄ + 2NaCl

So let's check out the chemical properties of the alkene family

1. Polymerization reaction

 What is polymerization?

Polymerization is the linking if smaller molecules called monomer to form a larger molecule called a polymer.

Alkenes like ethene undergo polymerization to form polythene by subjecting it go high temperature using

 2. Addition reaction

Alkenes undergo addition reaction to form a saturated hydrocarbon

e.g addition of hydrogen to ethane

C2H4   +    H2 ------->    C2H6

Ethene   hydrogen     ethane 

Ethane is the product formed and ethane is a saturated hydrocarbon

Guys, I hope you can do for the combustion of alkenes 

Question of the day?

• Why does alkene undergo addition reaction?

• Why does the alkene begin with ethene and not methane?

Post your answers in the comment section below and you are also free to ask questions just put your questions in the comment box.

Guys hope it helped. we will start from alkenes in my next post and please comment for any question, guide or help see you all in my next post guys…

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Thanks

Holuwarseun…