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Naming the alkenes

Give the IUPAC name for each of the following alkenes:

  1. CH 2 CHCH 2 CH 2 CH 3
  2. CH 3 CHCHCH 3

The properties of the alkenes

The properties of the alkenes are very similar to those of the alkanes, except that the alkenes are more reactive because they are unsaturated. As with the alkanes, compounds that have four or less carbon atoms are gases at room temperature, while those with five or more carbon atoms are liquids.

Reactions of the alkenes

Alkenes can undergo addition reactions because they are unsaturated. They readily react with hydrogen, water and the halogens. The double bond is broken and a single, saturated bond is formed. A new group is then added to one or both of the carbon atoms that previously made up the double bond. The following are some examples:

  1. A catalyst such as platinum is normally needed for these reactions H 2 C = C H 2 + H 2 H 3 C - C H 3 ( [link] )
    A hydrogenation reaction
  2. C H 2 = C H 2 + H B r C H 3 - C H 2 - B r ( [link] )
    A halogenation reaction
  3. C H 2 = C H 2 + H 2 O C H 3 - C H 2 - O H ( [link] )
    The formation of an alcohol

The alkenes

  1. Give the IUPAC name for each of the following organic compounds:
    1. CH 3 CHCH 2
  2. Refer to the data table below which shows the melting point and boiling point for a number of different organic compounds.
    Formula Name Melting point ( 0 C) Boiling point ( 0 C)
    C 4 H 10 Butane -138 -0.5
    C 5 H 12 Pentane -130 36
    C 6 H 14 Hexane -95 69
    C 4 H 8 Butene -185 -6
    C 5 H 10 Pentene -138 30
    C 6 H 12 Hexene -140 63
    1. At room temperature (approx. 25 0 C), which of the organic compounds in the table are:
      1. gases
      2. liquids
    2. In the alkanes...
      1. Describe what happens to the melting point and boiling point as the number of carbon atoms in the compound increases.
      2. Explain why this is the case.
    3. If you look at an alkane and an alkene that have the same number of carbon atoms...
      1. How do their melting points and boiling points compare?
      2. Can you explain why their melting points and boiling points are different?
    4. Which of the compounds, hexane or hexene, is more reactive? Explain your answer.
  3. The following reaction takes place: C H 3 C H C H 2 + H 2 C H 3 C H 2 C H 3
    1. Give the name of the organic compound in the reactants.
    2. What is the name of the product?
    3. What type of reaction is this?
    4. Which compound in the reaction is a saturated hydrocarbon?

The alkynes

In the alkynes, there is at least one triple bond between two of the carbon atoms. They are unsaturated compounds and are therefore highly reactive. Their general formula is C n H 2 n - 2 . The simplest alkyne is ethyne ( [link] ), also known as acetylene. Many of the alkynes are used to synthesise other chemical products.

Ethyne (acetylene)

Interesting fact

The raw materials that are needed to make acetylene are calcium carbonate and coal. Acetylene can be produced through the following reactions:

C a C O 3 C a O

C a O + 3 C C a C 2 + C O

C a C 2 + 2 H 2 O C a ( O H ) 2 + C 2 H 2

An important use of acetylene is in oxyacetylene gas welding. The fuel gas burns with oxygen in a torch. An incredibly high heat is produced, and this is enough to melt metal.

Naming the alkynes

The same rules will apply as for the alkanes and alkenes, except that the suffix of the name will now be -yne.

Give the IUPAC name for the following compound:

  1. There is a triple bond between two of the carbon atoms, so this compound is an alkyne. The suffix will be -yne. The triple bond is at the second carbon, so the suffix will in fact be 2-yne.

  2. If we count the carbons in a straight line, there are six. The prefix of the compound's name will be 'hex'.

  3. In this example, you will need to number the carbons from right to left so that the triple bond is between carbon atoms with the lowest numbers.

  4. There is a methyl (CH 3 ) group attached to the fifth carbon (remember we have numbered the carbon atoms from right to left).

  5. If we follow this order, the name of the compound is 5-methyl-hex-2-yne .

Got questions? Get instant answers now!

The alkynes

Give the IUPAC name for each of the following organic compounds.

  1. C 2 H 2
  2. CH 3 CH 2 CCH

Questions & Answers

how is ester formed
Aubrey Reply
how is n ester formed
Alcohol reacts with a carboxylic acid
an athlete with a mass of 70kg runs at a velocity of 45km . determine the athlete's momentum
Lesedi Reply
Is that a velocity or something else
45km/h i guess
Change to m/s
45km/h = 12.5 m/s p=mv =70×12.5 =875 kg.m/s
what are the measures of the rates of reaction
Lesego Reply
Volume Concentration Temperature Pressure Surface Area
the principle of superposition of waves
Sfundo Reply
what is work
Kool Reply
is this a group chat
Nobuhle Reply
Hey can y'all define newton's 2nd law
If a resultant force act on an object...the object will accelerate in the direction of a resultant force,the acceleration of the object is directly proportional to the net force and inversely proportional to the mass of the object
how do you calculate tension force
use the formula Fnet=ma if there is tension connecting two objects
to calculate Tension, usually calculate acceleration first Draw separate free body diagrams for each body. Apply Fnet = ma to calculate Tension
Hi people
how does temperature affect the equilibrium position
Blessing Reply
an increased temperature increases the average kinetic energy thus in turn increases the number of effective collisions........
so...which reaction is favored between endothermic and exothermic .when temperature is increased..?
exothermic reaction because energy is realised to the surroundings as heat and light energy ....graphical so much energy is realised as reactants to form product and because temperature is high rate of reaction is fast which means there is a successful collision
an object will continue in a state of rest unless it is acted upon an unbalanced force
Junior Reply
Newton's Law 1
First Newton's Law
Newton's first law
newton first law
Newton's first law
when pressure is increased what happen to volume
Siphelo Reply
care to explain?
if pressure is applied to a pistol , the volume will decrease and particles will collide more frequently with the wall of a container .Each time they collide with the wall they exert a force on them .More collision means more force and the pressure will increase , that Boyle's Law
Because the volume has decreased , the particle will collide more frequently with the wall of a container and each time they collide with the wall of a container they exert a force on them.More collision means more force so the pressure will increase , that Boyle's Law
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.
only gravitational force
no external force acting on an object
by only force of gravite
but gravitational force
a motion in which the only force acting is gravitational force
and an object experiencing free fall is referred as a projectile
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
Thats right
then Why ask when you Know the answer?
She's just helping those who forgot it...bro
guys I need help on Getting ready for a last minute test
Kenelioe Reply
what help you need
we'll I'm in grade 12 so we doing this topic about upac thing
on What?
the organic molecule section
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

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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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