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Organic macromolecules

As its name suggests, a macromolecule is a large molecule that forms when lots of smaller molecules are joined together. In this chapter, we will be taking a closer look at the structure and properties of different macromolecules, and at how they form.

Polymers

Some macromolecules are made up of lots of repeating structural units called monomers . To put it more simply, a monomer is like a building block. When lots of similar monomers are joined together by covalent bonds, they form a polymer . In an organic polymer , the monomers are joined by the carbon atoms of the polymer 'backbone'. A polymer can also be inorganic , in which case there may be atoms such as silicon in the place of carbon atoms. The key feature that makes a polymer different from other macromolecules, is the repetition of identical or similar monomers in the polymer chain. The examples shown below will help to make these concepts clearer.

Polymer

Polymer is a term used to describe large molecules consisting of repeating structural units, or monomers, connected by covalent chemical bonds.

  1. Polyethene Chapter [link] looked at the structure of a group of hydrocarbons called the alkenes . One example is the molecule ethene . The structural formula of ethene is is shown in [link] . When lots of ethene molecules bond together, a polymer called polyethene is formed. Ethene is the monomer which, when joined to other ethene molecules, forms the polymer polyethene . Polyethene is a cheap plastic that is used to make plastic bags and bottles.
    (a) Ethene monomer and (b) polyethene polymer
    A polymer may be a chain of thousands of monomers, and so it is impossible to draw the entire polymer. Rather, the structure of a polymer can be condensed and represented as shown in [link] . The monomer is enclosed in brackets and the 'n' represents the number of ethene molecules in the polymer, where 'n' is any whole number. What this shows is that the ethene monomer is repeated an indefinite number of times in a molecule of polyethene.
    A simplified representation of a polyethene molecule
  2. Polypropene Another example of a polymer is polypropene (fig [link] ). Polypropene is also a plastic, but is stronger than polyethene and is used to make crates, fibres and ropes. In this polymer, the monomer is the alkene called propene .
    (a) Propene monomer and (b) polypropene polymer

How do polymers form?

Polymers are formed through a process called polymerisation , where monomer molecules react together to form a polymer chain. Two types of polymerisation reactions are addition polymerisation and condensation polymerisation .

Polymerisation

In chemistry, polymerisation is a process of bonding monomers, or single units together through a variety of reaction mechanisms to form longer chains called polymers.

Addition polymerisation

In this type of reaction, monomer molecules are added to a growing polymer chain one at a time. No small molecules are eliminated in the process. An example of this type of reaction is the formation of polyethene from ethene (fig [link] ). When molecules of ethene are joined to each other, the only thing that changes is that the double bond between the carbon atoms in each ethene monomer is replaced by a single bond so that a new carbon-carbon bond can be formed with the next monomer in the chain. In other words, the monomer is an unsaturated compound which, after an addition reaction, becomes a saturated compound.

Questions & Answers

25 element of physics
musah Reply
an object will remain at rest or move at a constant velocity unless acted upon a net force
Lebogang Reply
thank you
Thabiso
law of inertia
Joan
an object resisting the change in velocity.
Thabiso
What is a molecule
Thabiso Reply
a molecule is a simplest structure unite of an elements
Else
thank you
Thabiso
Plz remind me the 1st Newton's law
Thabiso
Define the term functinal group of an organic compound
Kamvelihle Reply
a single atom or a group of atoms which is responsible for the property and function of an organic compound
Shandre
thanks😊
Kamvelihle
What's the relationship between intensity and the current?
Lufuno Reply
yu are Spi.ke spanish hola ele
Rolamf
cómo se llama el video donde disquete salgo yo
Rolamf
The intensity doesn't effect the current.
Mosa
what does the word emitted mean?
Mwinga Reply
to be ejected or released
Khathutshelo
Ok thanks
Mwinga
Released
Mosa
what are the hooke laws
Tyriek Reply
what's that
Mosa
what do really asked in exam
Leiyo Reply
questions
Kamvelihle
lmaooo
itsssjust
hi please help me how to balance redox reactions?
Brian Reply
Which equation do u wanna balance
Rifumo
i tried to write it but my phone just can't write it Cr2 O72-(aq) + H2S (aq) Cr3 (aq) + S(s)
Brian
show is the equation
Pride
us
Pride
hello. what is the difference between a primary, secondary and tertiary alcohol
Thokozani Reply
primary the C=bonded to 1 Carbon atom.... secondary=bonded to 2 carbon atoms tertiary=bonded to 3 carbon atoms
Christina
I hope you're answered
Christina
thanks Christina
Baningi
My pleasure
Christina
Thank you Christina. This is very helpful 😀👍👍💯
Thokozani
💯💯
Thokozani
Anytime Thokozani
Christina
How to calculate pH?
Thabo
thank you guys i didn't know about the primary, secondary and tertiary alcohols
Brian
thank you Christina
Brian
Hey guys which topic does AC nd DC generator falls
Phumelele
electrodynamics
Christina
thank you
Phumelele
can somebody help me with functional isomers
Baningi Reply
function isomer has the same molecular formula but different functional group
Thokozani
what's momentum
Luvelo Reply
the product of an objects mass times velocity. it is mainly prevalent in collisions.
tyrique
momentum
Sesethu
in order to produce an interference pattern, the waves used must be what?
Methane contains C and H. This compound is
Juan Reply
ketones's functional group
Moloi Reply
Why does the carboxyl group have acidc properties?
Evi Reply
carboxylic acids
tyrique

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Source:  OpenStax, Siyavula textbooks: grade 12 physical science. OpenStax CNX. Aug 03, 2011 Download for free at http://cnx.org/content/col11244/1.2
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