<< Chapter < Page Chapter >> Page >

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

what is the difference between momentum and a change in momentum?
Chavonne Reply
How to name a branched molecule from right or left?
Vadin Reply
What's Free Fall
Senzo Reply
Free Fall means there is no acting force on that object.
Dingaletu
only gravitational force
Dingaletu
no external force acting on an object
Sphiwe
by only force of gravite
Sello
but gravitational force
Sphiwe
true
Lucky
Do polymers form restrictedly only if compound is saturated, only?
milani Reply
what is a free fall?
Beyanca Reply
is when The Only Force acting On an Object is Gravitational Force
Madman
Thats right
Beyanca
then Why ask when you Know the answer?
Madman
She's just helping those who forgot it...bro
Thato
guys I need help on Getting ready for a last minute test
Kenelioe Reply
what help you need
Neil
we'll I'm in grade 12 so we doing this topic about upac thing
Kenelioe
on What?
Madman
the organic molecule section
Kenelioe
IUPAC NAMING WHICH FUNCTIONAL GROUP YOU CANNOT NAME?SO I COULD HELP YOU
Madman
ester
Sboniso
you should also look at structural isomers. Its crucial that they might add that one. also try and write down the structural formula of all the given compounds on the table
milani
hi guys i can explain everything in terms of physics and chemistry
Neil Reply
😂😂😂😂😂
Madman
yes
Lucky
yea
Kenelioe
guys 2mrrow I'm writing a test in chemistry I need help
Kenelioe
Hi guys. Can anyone please tell me what a functional group is?
Samukelo
a functional group depends on how many bonds there are between carbon atoms, if there are single bonds all the way it's an alkane, if there is a presence of at least one double bond it's a Alkene and if there's at least one triple bond it's an alkyne.
Olive
which quantity is measured in Watt?
Saara Reply
work
Absai
explain for me absai
Sboniso
is Power Not Work work is Measured In Joules it has Energy
Madman
thanks
Saara
Pleasure
Madman
what is galvanic cell ?
Oratile Reply
is an electrochemical cell that derives electrical energy from spontaneous redox reactions taking place within the cell.
Hope
how to understand alkane names
Sboniso Reply
suffix Ane in the IUPAC NAMING
Madman
elaborate a little more plz
Kenelioe
Alkanes are Saturated Meaning they don't have Multiple Bonds between Carbon Atoms and When you are Naming THEM THEY MUST END WITH (-ANE ) GET ME?
Madman
What are hydrocarbons
Phelo Reply
are organic Compounds with only Carbon and Hydrogen Atoms
Madman
whats the difference between aldehydes and ketones
Angel Reply
definition of chain parent
Lea Reply
what is wave?
Agness Reply
when butane burns in an excess of oxygen ,the products are
Slay
CO2 and H2O
GARY
Carbon dioxide and Water...
Thato
what is hydrocarbon
Ntswaki Reply
Hydrocarbon is a compostion of mainy carbon and hydrogen
Tsion
hydrocarbon compound made up of carbon and hydrogen only
Thembelani

Get the best Siyavula textbooks: gr... course in your pocket!





Source:  OpenStax, Siyavula textbooks: grade 12 physical science. OpenStax CNX. Aug 03, 2011 Download for free at http://cnx.org/content/col11244/1.2
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Siyavula textbooks: grade 12 physical science' conversation and receive update notifications?

Ask