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Doc Brown's Chemistry
Revising Organic Chemistry
The molecular structure and naming-nomenclature of
halogenoalkanes once known as 'haloalkanes' ('alkyl halides')
Part 1
Examples of displayed formula of halogenoalkanes, graphic
formula, molecular formula, skeletal formula, structural formula of this
homologous series
(1)The homologous
series of HALOGENOALKANES
of general formula CnH2n+1X (X = F, Cl, Br or I, n = 1,
2 or 3)
Examples of displayed formula of halogenoalkane
molecules, graphic
formula, molecular formula, skeletal formula, structural formula including isomers
of halogenoalkane molecules and some of the further halogen substitution products including CFCs,
HFCs and HCFCs
Revision notes for GCE Advanced
Subsidiary Level AS Advanced Level A2 IB
Revise AQA GCE Chemistry OCR GCE Chemistry Edexcel GCE Chemistry Salters
Chemistry CIE Chemistry revising courses for pre-university students
(equal to US grade 11 and grade 12 and Honours/honors level courses)
(2) more
haloalkanes of C4 * (3) more
haloalkanes_>C4_including cyclo..
Some 'old' and commercial
names are quoted in () though their use should be avoided if possible.
organic
chemical id tests * m/c
test on naming halogenoalkanes * type
in name test on halogenoalkanes
Intermolecular forces & boiling points of
halogenoalkanes compared to other
organic molecules
The shapes
and bond angles of simple molecules - section on bond angles in organic
molecules
A
brief guide to halogenoalkane nomenclature
- The generic suffix name (..ane) is based
on the longest carbon chain. 1 carbon, methane; 2 carbons, ethane;
3 carbons, propane; 4 carbons, butane. After these 4 preserved 'old
trivial' names, the name is 'numerically' systematic eg 5 carbons,
pentane; 6 hexane, 7 heptane etc.
- The halogenoalkane structures are based
on replacing one or more hydrogen atoms in the alkane structure
with a halogen atom X (X = F, Cl, Br or I).
- The positions of the substituent(s), denoted
with a prefix eg halo… or alkyl… groups, are denoted by using the
lowest possible numbers for the associated carbon atoms in the main
chain.
- If there is more than one 'type' of substituent
eg using the prefixes: bromo…, chloro…, methyl… etc., they are written
out in alphabetical order irrespective of carbon atom number (note:
di, tri are ignored in using this rule).
- The examples on this page are based on 1
to 3 carbon atoms
- Some 'old' and commercial names are quoted in () though their use should be avoided if possible [but many still used - just put one into GOGGLE!].
- A sub-CLASSIFICATION based on structural
differences, which can have chemical consequences on e.g. rate
of reaction or products formed in a reaction.
- Halogenoalkanes are classified according to
the atoms/groups attached to the carbon of the halogen atom X.
- Primary halogenoalkanes have the
structure R-CH2-X, R = H, alkyl, aryl etc. i.e.
apart from chloromethane they have one alkyl/aryl group attached
to the C of the C-X group.
- e.g. chloroethane CH3CH2Cl
- Secondary halogenoalkanes have
the structure R2CH-X, R = alkyl or aryl etc.
i.e. they have two alkyl/aryl groups attached to the C of the
C-X group.
- e.g. 2-bromobutane CH3CHBrCH2CH3
- Tertiary halogenoalkanes have the
structure R3C-X, R = alkyl or aryl etc. i.e. they
have three alkyl/aryl groups attached to the C of the C-X group.
- e.g. 2-iodo-2-methylpropane (CH3)3CI
-
NOTE:
Some 'old' and commercial names
are quoted in () though their use should be avoided if possible.
-
AND some abbrevations:
- CFC =
chloroflurocarbon (molecule consists of C, Cl, F atoms)
- HFC =
hydrofluorocarbon (molecule consists of C, H, F atoms)
- HCFC =
hydrochlorofluorocarbon (molecule consists of C, H, Cl, F atoms)
-
The shapes
and bond angles of simple molecules - section on bond angles in organic
molecules

Examples of non-cyclo
C1-3 HALOGENOALKANES
1. The simplest halogenoalkane is exemplified by
chloromethane
(methyl chloride), whose formula and structured are shown in 4 styles. (a) molecular formula, (b) abbreviated structural formula,
(c) ,
full structural formula, (d) '3D' representation of the structural formula.
2. to 7. Are examples of multi-substituted halogenoalkanes based on methane …
2. (a)
trichlorofluoromethane, (CFC-11, a chlorofluorocarbon or CFC),
(b) ,
chlorotrifluoromethane (a CFC)
3. (a)
dichlorodifluoromethane, (CFC-12),
(b) ,
dichlorofluoromethane (a HCFC)
4. difluoromethane
(a hydrofluorocarbon or
HFC, methylene difluoride)
5. tribromomethane
6. tetrachloromethane,
(carbon tetrachloride)
7. chlorodifluoromethane,
(HCFC-22
a hydrochlorofluorocarbon or
HCFC)
8. Bromoethane
(ethyl bromide) exemplifies the simplest mono-substituted alkane with 2 carbon atoms.
(a) molecular formula, (b) abbreviated
structural formula,
(c) more expanded structural formula, (d) full
graphic structural formula,
(e) '3D' structural formula, (f) skeletal formula
9. to 14., show a series of multi-substituted halogenoethane molecules (with the possibility of positional isomerism with only 2 carbon atoms) ...
9. (a) ,
1-chloro-1,1,2-trifluoroethane, (b) 2-chloro-1,1,1-trifluoromethane
(a HCFC), (c) ,
1-chloro-1,2-difluoroethane, (d) ,
2-chloro-1,1-difluoroethane, (e) ,
1-chloro-1,2,2-trifluoroethane
10. (a) ,
1-chloro-1-fluoroethane, (b) ,
1-chloro-2-fluoroethane, (c) ,
1-chloro-1,1-difluoroethane, (d) , 1,1,2-trichloro-1,2,2-trifluoroethane
(CFC-113)
11. 2,2-dichloro-1,1,1-trifluoroethane
(HCFC-123)
12. (a) ,
1,1-difluoroethane
(HFC-152a), (b) ,
1,2-difluoroethane
13. (a) ,
1,1-dichloro-1-fluoroethane
(HCFC-141b), (b) ,
1,1-dichloro-2,2-difluoroethane
14.(a)
1,1,1-trifluoroethane, (b) ,
1,1,2-trifluoroethane, (c) 1,1,1,2-tetrafluoroethane
(HFC-134a), (d) ,
1,1,2,2-tetrafluoroethane
with 3 carbon atoms you get positional isomerism with only 1 halogen atom (1- or 2- …)
15. (a) , (b) , (c) ,
1-bromopropane
(propyl bromide)
16. (a) , (b) , (c) , (d) ,
2-bromopropane
(isopropyl bromide)
17.(a) , (b) , (c) ,
2-chloropropane
(isopropyl chloride)
18.(a) , (b) , (c) , (d) ,
1-iodopropane
(propyl iodide)
19. With 2 like halogen atoms there are four positional isomers
(a) , , ,
1,1-dichloropropane
(b) , , ,
1,2-dichloropropane
(c) , , ,
1,3-dichloropropane
(d) , , ,
2,2-dichloropropane
20. with 3 like halogen atoms there are 5 positional isomers
(a) , , ,
1,1,1-trifluoropropane
(b) , , ,
1,1,2-trifluoropropane
(c) , , ,
1,1,3-trifluoropropane
(d) , , ,
1,2,2-trifluoropropane
(e) , , ,
1,2,3-trifluoropropane

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