Transcript Functional groups

- Functional Groups
- Halogens, Alcohols & Ethers
Mr. Shields
Regents Chemistry
U17 L01
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Functional Groups
Besides hydrogen or carbon bonded to carbon
Many other atoms can bond to carbon and these
Lead to the formation of what are called
“Functional groups”
Each Functional group has it’s own unique chemical
And physical properties
So what are these different fuctional groups?
Let’s take a look.
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Check out Table R in your Reference Table.
We’ll take a look
at all of these
Groups in time
But right now we’re
going to focus on…
-Halides
-Alcohols
-Ethers
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Organic Halides
• These compounds are often called halocarbons
or the Halides
• One or more hydrogen atoms in an alkane is
replaced with a halogen
– F, Cl, Br, or I
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Properties of Alkyl Halides
 Alkyl halides are extremely unreactive
-Often used when chemical inertness
is important
-Examples: CFC’s (refrigerants, Aerosol
propellants, Teflon (polymer), Brominated
compounds (Fire retardant clothing)
- many of these compounds are now banned
from use for health and environmental
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reasons.
Properties of Alkyl Halides
 Alkyl halides due to there high molecular wt. & stronger
IMF have considerably higher B.P. and greater density
than their corresponding alkanes
Propane
Chloropropane
Bromopropane
B.P. (deg. C)
-42
47
71
Density (g/ml)
(Gas)
.890
1.335
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Naming Organic Halides
Use these prefixes to specify the substituent:
– fluoro, chloro, bromo, iodo
– Name substituents in alphabetical order
• If necessary, give locations by numbering C-atoms in
longest backbone so that the halide has the lowest #
– Keep halide alphbetical order.
• If more than one, use di, tri, etc. to specify # of
substituents.
c-c-c-c-c
Br Br
2,3-dibromopentane
Not
3,4-dibromopentane
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Naming Halides
CH3Cl
H
H–C–Cl
H
Chloromethane
“Chloroform”
CH3CHFCHBr2
H H Br
H–C–C–C–Br
H F H
1,1-dibromo-2-fluoropropane
C3H5Br2F
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Name this compound:
3-Bromo-2-Iodopentane
Name this compound:
F
H-C
F
Cl
1,1-dicloro-2,2-difluoroethane
Cl
One of the “freons”
C-H
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Alcohols
• Alcohols contain the polar -OH functional group
– OH groups are capable of Hydrogen bonding
– The –OH group is sometimes referred to as a Hydroxyl group
• This polar functional group affects physical properties
– B.P is much higher than the corresponding Alkane
• Ethanol (C2H5OH) +78C // Ethane (C2H6) -89C
– Low Mol. Wt. Alcohols are very soluble in water
– Ethanol is totally miscible in water, Hexanol sol. is 0.59g/100 ml
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Hydroxyl groups
Alcohols can hydrogen bond because they have a
Hydrogen atom that is bonded to oxygen.
This results in
Much higher B.P.’s
And higher water
solubulity
CH3–CH2–O-H
CH3–CH2–O-H
H-O-H
Remember… Alcohols are neither acids nor bases (they do
not ionize in water to either H+ or OH-)
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Types of Alcohols
• An –OH attached to a terminal Carbon atom (-CH2-OH) is
called a primary alcohol
• An –OH attached to an internal carbon with a hydrogen
atom also attached to that carbon (-CHOH-) is called a
secondary alcohol
• An –OH attached to an internal carbon that is attached to 3
other carbons is called a tertiary alcohol
Ethanol (primary)
2-propanol (secondary)
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Naming Alcohols
• Select as the parent structure the longest continuous
carbon chain that contains the –OH
• Drop the –e from the alkane name of the carbon chain and
add –ol
• Indicate by a number (if necessary) the position of the –OH
group
ethanol
2-propanol
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Diols
• Diols, like dienes have 2
functional groups
• There are Two –OH
groups (dihydroxy)
• Instead of ending in “ol”
the name ends in “diol”
• Example on left –
2,2 - propanediol
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Triols
• There are three –OH groups
- Add suffix –triol to name
Glycerine (common name) is actually a “Triol”
• 1,2,3 –propanetriol (Glycerol)
OH OH OH
H2C—- CH —CH2
• Known also as Tri-hydroxy alcohols
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Ethers
 Even though ethers have an oxygen atom in their structure
They are unable to form hydrogen bonds with themselves
- alkyl groups are bonded directly to Oxygen
- No hydrogen directly bonded to Oxygen
 Ethers are not linear, They have a bent shape similar to water
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Ether’s Properties
 BP’s tend to be low
Comparable to similar MW hydrocarbons
No H-bonding possible ether to ether
 Solubility in water is reasonably high for lower
M.W. ethers
H-Bonding to Water is possible
Propane
Dimethylether
Diethylether
M.W.
44
46
74
B.P. (deg. C)
-42
-24
35
Sol in Water
(g/100 ml)
8
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Naming Ethers
(common names)
Ethylmethyl ether
• Name the alkyl groups on either side and add ether to the end.
• List attached alkyl groups in alphabetical order
– If the alkyl group is the same the alkyl group is prefaced by “Di” followed
by “ether”. (Ex. Diethyl ether)
• NO NUMBERS NEEDED to designate location of Oxygen!
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Naming Ethers
Notice that Table R lists
This name incorrectly
Name this compound:
Dimethyl ether
Name this compound:
Ethylpropyl ether
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