In the previous section, we saw the nomenclature of organic compounds carrying the Carboxyl group. In this section, we will see the Halo group.
• We know that halogens are one of the several 'families' in the periodic table.
• We have also other families like oxygen family, carbon family, noble gases etc., Details here.
• Some members of the halogen family forms compounds with hydrocarbons. Such compounds are called halo compounds
• We will now see them in detail:
■ The members of the halogen family which form compounds with hydrocarbons are:
Fluorine (F), Chlorine (Cl), Bromine (Br) and Iodine (I)
■ When a halogen become part of the organic compound, it is called a halo group
So we have: Fluoro group (ㅡF), Chloro group (ㅡCl), Bromo group (ㅡBr) and Iodo group (ㅡI)
Now we will see the IUPAC names of halo compounds.
• The rules are very similar to the ones that we saw for branched chain hydrocarbons. Details here.
So we can write:
• The position of carbon atom carrying the halo group+hyphen+name of halo group+word root+suffix
♦ The halo group should be given the lowest possible number
• Let us see a solved example:
Solved example 14.11
Write the IUPAC name of the compounds given in fig.14.76 below:
Solution:
We will write the steps:
Case (i):
1. In the given compound, there are 3 carbon atoms. So the word root is prop
There are only single bonds. So the suffix is ane
2. The numbering should be done towards the left from the right most carbon atom. This is to ensure that, the carbon atom carrying the halo group gets the lowest number.
• Thus the carbon atom carrying the halo group gets number 1
3. Name of the halo group is Chloro
4. Now we can assemble the name. The rule is:
The position of halo group+hyphen+name of halo group+word root+suffix
• Thus we get: 1-Chloropropane.
Case (ii):
1. In the given compound, there are 2 carbon atoms. So the word root is eth
There are only single bonds. So the suffix is ane
2. The numbering should be done towards the left from the right most carbon atom. This is to ensure that, the halo group gets the lowest number.
• Thus the halo group gets number 1
3. Name of the halo group is bromo
4. Now we can assemble the name. The rule is:
The position of halo group+hyphen+name of halo group+word root+suffix
• Thus we get: 1-Bromoethane.
Case (iii):
1. In the given compound, there is only one carbon atom. So the word root is meth
There are only single bonds. So the suffix is ane
2. Numbering is not required since there is only one carbon atom.
3. Name of the halo group is Bromo
4. Now we can assemble the name. The rule is:
The position of halo group+hyphen+name of halo group+word root+suffix
There is no need to write the position number because, only one position is possible
• Thus we get: Bromomethane.
Case (iv):
1. In the given compound, there are 3 carbon atoms. So the word root is prop
There are only single bonds. So the suffix is ane
2. The numbering can be done either from left or right. Both will give the position as 2
3. Name of the halo group is Chloro
4. Now we can assemble the name. The rule is:
The position of halo group+hyphen+name of halo group+word root+suffix
• Thus we get: 2-Chloropropane.
Case (v):
1. In the given compound, there are 5 carbon atoms. So the word root is pent
There are only single bonds. So the suffix is ane
2. The numbering should be done towards the left from the right most carbon atom. This is to ensure that, carbon atom carrying the halo group gets the lowest number.
• Thus the carbon atom carrying the halo group gets number 2
3. Name of the halo group is Chloro
4. Now we can assemble the name. The rule is:
The position of halo group+hyphen+name of halo group+word root+suffix
• Thus we get: 2-Chloropentane.
Now we will see the IUPAC names of compounds with more than one halo group.
• The rules are similar to those when more than one branch is present. We saw the details here.
So we can write:
[Position number of carbon atom carrying the group+hyphen+name of halo group]
+hyphen
+[Position number of carbon atom carrying the group+hyphen+name of halo group]
+word root+suffix
• The items inside square brackets are related to halo groups. Those groups should be written in alphabetical order.
♦ But in our present discussion, we will encounter those compounds only in which there is only one type of halo group. So we do not need to worry about alphabetical order.
Solved example 14.12
Write the IUPAC name of the halo compounds given in fig.14.77 below:
Solution:
We will write the steps:
Case (i):
1. In the given compound, there are 4 carbon atoms. So the word root is But
There are only single bonds. So the suffix is ane
2. The numbering can be done either from left or right. Both will give the position as 2 for the first halo group
• Thus the first halo group gets number 2 and the second halo group gets number 3
3. Name of the halo group is Chloro
4. Now we can assemble the name. The rule is:
[Position number of carbon atom carrying the group+hyphen+name of halo group]
+hyphen
+[Position number of carbon atom carrying the group+hyphen+name of halo group]
+word root+suffix
• Thus we get:
[2-chloro]
+hyphen
[3-chloro]
+butane
So the name would be: 2-Chloro-3-chlorobutane
But . . .
As we have seen in the case of repeating branches, we can write:
• If a group comes two times, it's name should not be written two times
♦ Instead, the prefix 'di' should be used
• If a group comes three times, it's name should not be written three times
♦ Instead, the prefix 'tri' should be used
• If a group comes four times, it's name should not be written four times
♦ Instead, the prefix 'tetra' should be used
so on . . .
• The positions should be separated by commas
So the name of our compound is:
2,3-Dichlorobutane.
Case (ii):
1. In the given compound, there are 5 carbon atoms. So the word root is pent
There are only single bonds. So the suffix is ane
2. The numbering can be done either from left or right. Both will give the position as 2 for the first halo group
• Thus the first halo group gets number 2 and the second halo group gets number 4
3. Name of the halo group is Chloro
4. Now we can assemble the name. The rule is:
[Position number of carbon atom carrying the group+hyphen+name of halo group]
+hyphen
+[Position number of carbon atom carrying the group+hyphen+name of halo group]
+word root+suffix
• Thus we get:
[2-chloro]
+hyphen
[4-chloro]
+pentane
So the name would be: 2-Chloro-4-chloropentane
But . . .
As we have seen in the previous case, we can write:
• If a group comes two times, it's name should not be written two times
♦ Instead, the prefix 'di' should be used
• If a group comes three times, it's name should not be written three times
♦ Instead, the prefix 'tri' should be used
• If a group comes four times, it's name should not be written four times
♦ Instead, the prefix 'tetra' should be used
so on . . .
• The positions should be separated by commas
So the name of our compound is:
2,4-Dichloropentane.
Solved example 14.13
Write the IUPAC name of the compounds given in fig.14.78 below:
Solution:
We will write the steps:
Case (i):
1. In the given compound, there are 3 carbon atoms. So the word root is prop
There are only single bonds. So the suffix is ane
2. The numbering should be done towards the left from the right most carbon atom. This is to ensure that, the carbon atom carrying the groups gets the lowest number.
• Thus the carbon atom carrying the halo groups gets number 2
3. Name of the halo group is Chloro
4. Now we can assemble the name. The rule is:
[Position number of branch+hyphen+name of halo group]
+hyphen
+[Position number of branch+hyphen+name of halo group]
+word root+suffix
• Thus we get:
[2-chloro]
+hyphen
[2-chloro]
+butane
So the name would be: 2-Chloro-2-chlorobutane
But . . .
As we have seen in the previous case, we can write:
• If a group comes two times, it's name should not be written two times
♦ Instead, the prefix 'di' should be used
• If a group comes three times, it's name should not be written three times
♦ Instead, the prefix 'tri' should be used
• If a group comes four times, it's name should not be written four times
♦ Instead, the prefix 'tetra' should be used
so on . . .
• The positions should be separated by commas.
• If the groups are at the same position, the position number should be repeated.
So the name of our compound is:
2,2-Dichlorobutane.
Case (ii):
1. In the given compound, there are 4 carbon atoms. So the word root is but
There are only single bonds. So the suffix is ane
2. The numbering can be done either from left or right. Both will give the position as 2 for the carbon carrying the halo groups
• Thus the carbon atom carrying the halo groups gets number 2
3. Name of the halo group is Chloro
4. Now we can assemble the name. The rule is:
[Position number of branch+hyphen+name of halo group]
+hyphen
+[Position number of branch+hyphen+name of halo group]
+word root+suffix
• Thus we get:
[2-chloro]
+hyphen
[2-chloro]
+propane
So the name would be: 2-Chloro-2-chloropropane
But . . .
As we have seen in the previous case, we can write:
• If a group comes two times, it's name should not be written two times
♦ Instead, the prefix 'di' should be used
• If a group comes three times, it's name should not be written three times
♦ Instead, the prefix 'tri' should be used
• If a group comes four times, it's name should not be written four times
♦ Instead, the prefix 'tetra' should be used
so on . . .
• The positions should be separated by commas.
• If the groups are at the same position, the position number should be repeated.
So the name of our compound is:
2,2-Dichloropropane.
Case (iii):
1. In the given compound, there are 4 carbon atoms. So the word root is but
There are only single bonds. So the suffix is ane
2. The numbering can be done in two ways:
• When numbered from left to right, the position numbers are 2,3,3
♦ This gives a sum of: 2+3+3 = 8
• When numbered from right to left, the position numbers are 2,2,3
♦ This gives a sum of: 2+2+3 = 7
• The numbering from right to left gives a lower sum. So it should be adopted.
• The above rule is known as the sum rule. We will see more details about it in higher classes.
3. Name of the halo group is Bromo
4. Now we can assemble the name. The rule is:
[Position number of branch+hyphen+name of halo group]
+hyphen
+[Position number of branch+hyphen+name of halo group]
+word root+suffix
• Thus we get:
[2-bromo]
+hyphen
[2-bromo]
+hyphen
[3-bromo]
+butane
So the name would be: 2-bromo-2-bromo-3-bromobutane
But . . .
As we have seen in the previous cases, we can write:
• If a group comes two times, it's name should not be written two times
♦ Instead, the prefix 'di' should be used
• If a group comes three times, it's name should not be written three times
♦ Instead, the prefix 'tri' should be used
• If a group comes four times, it's name should not be written four times
♦ Instead, the prefix 'tetra' should be used
so on . . .
• The positions should be separated by commas.
• If the groups are at the same position, the position number should be repeated.
So the name of our compound is:
2,2,3-Tribromobutane.
Now we will see the reverse process. That is., we are given the IUPAC name of a halo compound. We must write the structural formula. We will learn the method by analysing an example:
1. Given IUPAC name is: 2-Chloropropane
2. Consider the word root. It is prop. So there are 3 carbon atoms
3. Consider the suffix. It is ane. So the compound is derived from an alkane
• So all the carbon-carbon bonds are single bonds
4. So we have 3 carbon atoms with single bonds between them. The numbering (from left to right) can also be done at this stage. This is shown in fig.14.79(a) below:
5. The halo group is at position 2.
So we attach the ㅡCl to the second carbon atom. This is shown in fig(b)
6. Fill all the valencies of carbon atoms.
• We use hydrogen to fill up the valencies.
• The result is shown in fig.14.79(c) above. So this fig.14.79(c) shows the required structure
Another example:
1. Given IUPAC name is: 2,3-Dibromopentane
2. Consider the word root. It is pent. So there are 5 carbon atoms
3. Consider the suffix. It is ane. So the compound is derived from an alkane
• So all the carbon-carbon bonds are single bonds
4. So we have 5 carbon atoms with single bonds between them. The numbering (from left to right) can also be done at this stage. This is shown in fig.14.80(a) below:
5. The halo groups are at positions 2 and 3.
So we attach the ㅡBr to the second and third carbon atoms. This is shown in fig(b)
6. Fill all the valencies of carbon atoms.
• We use hydrogen to fill up the valencies.
• The result is shown in fig.14.80(c) above. So this fig.14.80(c) shows the required structure
■ In the first section in this chapter, we saw how the 'alkyl radical' gets itself attached to an open chain. See details here.
■ In a previous section, we saw how a 'hydroxyl group' that is., 'ㅡOH', gets itself attached to an open chain. See details here.
■ In another previous section, we saw how an 'aldehyde group' that is., 'ㅡCHO', gets itself attached to an open chain. See details here.
■ In yet another previous section, we saw how a 'keto group' that is., 'ㅡCO', gets itself attached to an open chain. See details here.
■ In the just previous section we saw how a 'carboxyl group' that is., 'ㅡCOOH', gets itself attached to an open chain. See details here.
■ Now we will see the same for the halo group:
• Though there are different members (fluoro, chloro etc.,) in the halo group, the bonding details are same for all. So we will take chlorine as an example
• We have seen the bonding between sodium and chlorine to form sodium chloride. it is an ionic bond. Details here.
• We have also seen the covalent bonding between two chlorine atoms. Two chlorine atoms share a pair of electrons between them to achieve octet and thus stability.
• It can be represented as: ClㅡCl. Details here. The two chlorine atoms bonded together by a single covalent bond becomes a chlorine molecule (Cl2)
• So when a chlorine atom is removed from the chlorine molecule, the remaining portion becomes a chloro group (ㅡCl). It will be unstable and will be looking for an electron.
• If a hydrogen atom is removed from a hydrocarbon, the ㅡCl can take it's place. This is shown in fig.14.81 below:
• Thus we get a stable molecule
In the next section, we will see the Alkoxy group.
• We know that halogens are one of the several 'families' in the periodic table.
• We have also other families like oxygen family, carbon family, noble gases etc., Details here.
• Some members of the halogen family forms compounds with hydrocarbons. Such compounds are called halo compounds
• We will now see them in detail:
■ The members of the halogen family which form compounds with hydrocarbons are:
Fluorine (F), Chlorine (Cl), Bromine (Br) and Iodine (I)
■ When a halogen become part of the organic compound, it is called a halo group
So we have: Fluoro group (ㅡF), Chloro group (ㅡCl), Bromo group (ㅡBr) and Iodo group (ㅡI)
Now we will see the IUPAC names of halo compounds.
• The rules are very similar to the ones that we saw for branched chain hydrocarbons. Details here.
So we can write:
• The position of carbon atom carrying the halo group+hyphen+name of halo group+word root+suffix
♦ The halo group should be given the lowest possible number
• Let us see a solved example:
Solved example 14.11
Write the IUPAC name of the compounds given in fig.14.76 below:
 |
| Fig.14.76 |
We will write the steps:
Case (i):
1. In the given compound, there are 3 carbon atoms. So the word root is prop
There are only single bonds. So the suffix is ane
2. The numbering should be done towards the left from the right most carbon atom. This is to ensure that, the carbon atom carrying the halo group gets the lowest number.
• Thus the carbon atom carrying the halo group gets number 1
3. Name of the halo group is Chloro
4. Now we can assemble the name. The rule is:
The position of halo group+hyphen+name of halo group+word root+suffix
• Thus we get: 1-Chloropropane.
Case (ii):
1. In the given compound, there are 2 carbon atoms. So the word root is eth
There are only single bonds. So the suffix is ane
2. The numbering should be done towards the left from the right most carbon atom. This is to ensure that, the halo group gets the lowest number.
• Thus the halo group gets number 1
3. Name of the halo group is bromo
4. Now we can assemble the name. The rule is:
The position of halo group+hyphen+name of halo group+word root+suffix
• Thus we get: 1-Bromoethane.
Case (iii):
1. In the given compound, there is only one carbon atom. So the word root is meth
There are only single bonds. So the suffix is ane
2. Numbering is not required since there is only one carbon atom.
3. Name of the halo group is Bromo
4. Now we can assemble the name. The rule is:
The position of halo group+hyphen+name of halo group+word root+suffix
There is no need to write the position number because, only one position is possible
• Thus we get: Bromomethane.
Case (iv):
1. In the given compound, there are 3 carbon atoms. So the word root is prop
There are only single bonds. So the suffix is ane
2. The numbering can be done either from left or right. Both will give the position as 2
3. Name of the halo group is Chloro
4. Now we can assemble the name. The rule is:
The position of halo group+hyphen+name of halo group+word root+suffix
• Thus we get: 2-Chloropropane.
Case (v):
1. In the given compound, there are 5 carbon atoms. So the word root is pent
There are only single bonds. So the suffix is ane
2. The numbering should be done towards the left from the right most carbon atom. This is to ensure that, carbon atom carrying the halo group gets the lowest number.
• Thus the carbon atom carrying the halo group gets number 2
3. Name of the halo group is Chloro
4. Now we can assemble the name. The rule is:
The position of halo group+hyphen+name of halo group+word root+suffix
• Thus we get: 2-Chloropentane.
Now we will see the IUPAC names of compounds with more than one halo group.
• The rules are similar to those when more than one branch is present. We saw the details here.
So we can write:
[Position number of carbon atom carrying the group+hyphen+name of halo group]
+hyphen
+[Position number of carbon atom carrying the group+hyphen+name of halo group]
+word root+suffix
• The items inside square brackets are related to halo groups. Those groups should be written in alphabetical order.
♦ But in our present discussion, we will encounter those compounds only in which there is only one type of halo group. So we do not need to worry about alphabetical order.
Solved example 14.12
Write the IUPAC name of the halo compounds given in fig.14.77 below:
 |
| Fig.14.77 |
We will write the steps:
Case (i):
1. In the given compound, there are 4 carbon atoms. So the word root is But
There are only single bonds. So the suffix is ane
2. The numbering can be done either from left or right. Both will give the position as 2 for the first halo group
• Thus the first halo group gets number 2 and the second halo group gets number 3
3. Name of the halo group is Chloro
4. Now we can assemble the name. The rule is:
[Position number of carbon atom carrying the group+hyphen+name of halo group]
+hyphen
+[Position number of carbon atom carrying the group+hyphen+name of halo group]
+word root+suffix
• Thus we get:
[2-chloro]
+hyphen
[3-chloro]
+butane
So the name would be: 2-Chloro-3-chlorobutane
But . . .
As we have seen in the case of repeating branches, we can write:
• If a group comes two times, it's name should not be written two times
♦ Instead, the prefix 'di' should be used
• If a group comes three times, it's name should not be written three times
♦ Instead, the prefix 'tri' should be used
• If a group comes four times, it's name should not be written four times
♦ Instead, the prefix 'tetra' should be used
so on . . .
• The positions should be separated by commas
So the name of our compound is:
2,3-Dichlorobutane.
Case (ii):
1. In the given compound, there are 5 carbon atoms. So the word root is pent
There are only single bonds. So the suffix is ane
2. The numbering can be done either from left or right. Both will give the position as 2 for the first halo group
• Thus the first halo group gets number 2 and the second halo group gets number 4
3. Name of the halo group is Chloro
4. Now we can assemble the name. The rule is:
[Position number of carbon atom carrying the group+hyphen+name of halo group]
+hyphen
+[Position number of carbon atom carrying the group+hyphen+name of halo group]
+word root+suffix
• Thus we get:
[2-chloro]
+hyphen
[4-chloro]
+pentane
So the name would be: 2-Chloro-4-chloropentane
But . . .
As we have seen in the previous case, we can write:
• If a group comes two times, it's name should not be written two times
♦ Instead, the prefix 'di' should be used
• If a group comes three times, it's name should not be written three times
♦ Instead, the prefix 'tri' should be used
• If a group comes four times, it's name should not be written four times
♦ Instead, the prefix 'tetra' should be used
so on . . .
• The positions should be separated by commas
So the name of our compound is:
2,4-Dichloropentane.
Solved example 14.13
Write the IUPAC name of the compounds given in fig.14.78 below:
 |
| Fig.14.78 |
We will write the steps:
Case (i):
1. In the given compound, there are 3 carbon atoms. So the word root is prop
There are only single bonds. So the suffix is ane
2. The numbering should be done towards the left from the right most carbon atom. This is to ensure that, the carbon atom carrying the groups gets the lowest number.
• Thus the carbon atom carrying the halo groups gets number 2
3. Name of the halo group is Chloro
4. Now we can assemble the name. The rule is:
[Position number of branch+hyphen+name of halo group]
+hyphen
+[Position number of branch+hyphen+name of halo group]
+word root+suffix
• Thus we get:
[2-chloro]
+hyphen
[2-chloro]
+butane
So the name would be: 2-Chloro-2-chlorobutane
But . . .
As we have seen in the previous case, we can write:
• If a group comes two times, it's name should not be written two times
♦ Instead, the prefix 'di' should be used
• If a group comes three times, it's name should not be written three times
♦ Instead, the prefix 'tri' should be used
• If a group comes four times, it's name should not be written four times
♦ Instead, the prefix 'tetra' should be used
so on . . .
• The positions should be separated by commas.
• If the groups are at the same position, the position number should be repeated.
So the name of our compound is:
2,2-Dichlorobutane.
Case (ii):
1. In the given compound, there are 4 carbon atoms. So the word root is but
There are only single bonds. So the suffix is ane
2. The numbering can be done either from left or right. Both will give the position as 2 for the carbon carrying the halo groups
• Thus the carbon atom carrying the halo groups gets number 2
3. Name of the halo group is Chloro
4. Now we can assemble the name. The rule is:
[Position number of branch+hyphen+name of halo group]
+hyphen
+[Position number of branch+hyphen+name of halo group]
+word root+suffix
• Thus we get:
[2-chloro]
+hyphen
[2-chloro]
+propane
So the name would be: 2-Chloro-2-chloropropane
But . . .
As we have seen in the previous case, we can write:
• If a group comes two times, it's name should not be written two times
♦ Instead, the prefix 'di' should be used
• If a group comes three times, it's name should not be written three times
♦ Instead, the prefix 'tri' should be used
• If a group comes four times, it's name should not be written four times
♦ Instead, the prefix 'tetra' should be used
so on . . .
• The positions should be separated by commas.
• If the groups are at the same position, the position number should be repeated.
So the name of our compound is:
2,2-Dichloropropane.
Case (iii):
1. In the given compound, there are 4 carbon atoms. So the word root is but
There are only single bonds. So the suffix is ane
2. The numbering can be done in two ways:
• When numbered from left to right, the position numbers are 2,3,3
♦ This gives a sum of: 2+3+3 = 8
• When numbered from right to left, the position numbers are 2,2,3
♦ This gives a sum of: 2+2+3 = 7
• The numbering from right to left gives a lower sum. So it should be adopted.
• The above rule is known as the sum rule. We will see more details about it in higher classes.
3. Name of the halo group is Bromo
4. Now we can assemble the name. The rule is:
[Position number of branch+hyphen+name of halo group]
+hyphen
+[Position number of branch+hyphen+name of halo group]
+word root+suffix
• Thus we get:
[2-bromo]
+hyphen
[2-bromo]
+hyphen
[3-bromo]
+butane
So the name would be: 2-bromo-2-bromo-3-bromobutane
But . . .
As we have seen in the previous cases, we can write:
• If a group comes two times, it's name should not be written two times
♦ Instead, the prefix 'di' should be used
• If a group comes three times, it's name should not be written three times
♦ Instead, the prefix 'tri' should be used
• If a group comes four times, it's name should not be written four times
♦ Instead, the prefix 'tetra' should be used
so on . . .
• The positions should be separated by commas.
• If the groups are at the same position, the position number should be repeated.
So the name of our compound is:
2,2,3-Tribromobutane.
Now we will see the reverse process. That is., we are given the IUPAC name of a halo compound. We must write the structural formula. We will learn the method by analysing an example:
1. Given IUPAC name is: 2-Chloropropane
2. Consider the word root. It is prop. So there are 3 carbon atoms
3. Consider the suffix. It is ane. So the compound is derived from an alkane
• So all the carbon-carbon bonds are single bonds
4. So we have 3 carbon atoms with single bonds between them. The numbering (from left to right) can also be done at this stage. This is shown in fig.14.79(a) below:
 |
| Fig.14.79 |
So we attach the ㅡCl to the second carbon atom. This is shown in fig(b)
6. Fill all the valencies of carbon atoms.
• We use hydrogen to fill up the valencies.
• The result is shown in fig.14.79(c) above. So this fig.14.79(c) shows the required structure
Another example:
1. Given IUPAC name is: 2,3-Dibromopentane
2. Consider the word root. It is pent. So there are 5 carbon atoms
3. Consider the suffix. It is ane. So the compound is derived from an alkane
• So all the carbon-carbon bonds are single bonds
4. So we have 5 carbon atoms with single bonds between them. The numbering (from left to right) can also be done at this stage. This is shown in fig.14.80(a) below:
 |
| Fig.14.80 |
So we attach the ㅡBr to the second and third carbon atoms. This is shown in fig(b)
6. Fill all the valencies of carbon atoms.
• We use hydrogen to fill up the valencies.
• The result is shown in fig.14.80(c) above. So this fig.14.80(c) shows the required structure
■ In the first section in this chapter, we saw how the 'alkyl radical' gets itself attached to an open chain. See details here.
■ In a previous section, we saw how a 'hydroxyl group' that is., 'ㅡOH', gets itself attached to an open chain. See details here.
■ In another previous section, we saw how an 'aldehyde group' that is., 'ㅡCHO', gets itself attached to an open chain. See details here.
■ In yet another previous section, we saw how a 'keto group' that is., 'ㅡCO', gets itself attached to an open chain. See details here.
■ In the just previous section we saw how a 'carboxyl group' that is., 'ㅡCOOH', gets itself attached to an open chain. See details here.
■ Now we will see the same for the halo group:
• Though there are different members (fluoro, chloro etc.,) in the halo group, the bonding details are same for all. So we will take chlorine as an example
• We have seen the bonding between sodium and chlorine to form sodium chloride. it is an ionic bond. Details here.
• We have also seen the covalent bonding between two chlorine atoms. Two chlorine atoms share a pair of electrons between them to achieve octet and thus stability.
• It can be represented as: ClㅡCl. Details here. The two chlorine atoms bonded together by a single covalent bond becomes a chlorine molecule (Cl2)
• So when a chlorine atom is removed from the chlorine molecule, the remaining portion becomes a chloro group (ㅡCl). It will be unstable and will be looking for an electron.
• If a hydrogen atom is removed from a hydrocarbon, the ㅡCl can take it's place. This is shown in fig.14.81 below:
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| Fig.14.81 |
In the next section, we will see the Alkoxy group.
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