Download Organic Functional Groups

Organic Functional Groups (12U Chem Nelson)
Def’n – a structural arrangement of atoms that imparts particular
characteristics to the molecule (eg solubility, polarity, mp,bp,
reactivity, etc)
- molecules with similar characteristics (due to this structure) are
grouped into an organic family (eg alcohols)
How to Recognize them
1) carbon-carbon multiple bonds (alkenes, alkynes)
2) Single bonds between CARBON and a more electronegative atom
Eg
C
O
C
N
C
Cl
3) carbon atom double bonded to an oxygen atom
C═O
(called a “carbonyl” group)
Priority List (low to high - for nomenclature naming rules)
1)
2)
3)
4)
5)
6)
7)
8)
9)
alkyl, halogen (RX), aromatic, nitro (RNO2)
alkyne
alkene
amino (RNH2)
alcohol (ROH)
ketone (RCOR1)
aldehyde (RCOH)
ester (RCOOR1)
carboxylic acid (RCOOH)
Organic Halides (1.1)
1) found in refrigerants (CFC’s), cookware (Teflon), insecticides (DDT),
medical disinfectants (“hexachlorophene”) and electrical transformers
(PCB’s)
2) carcinogenic concerns, some toxic, air pollution/ozone hole
eg. “TCE” (or trichloroethylene) is used as a dry cleaning solvent. It
forms free radicals and is pervasive in our water supply due to its density
and polarity.
Nomenclature aka
Prefix
X=F
Cl
Br
I
eg
fluoro
chloro
bromo
iodo
alkyl halides “R-X”
(R= alkyl part)
CH2 ---CH2
Br
Br
1,2-dibromoethane
Note – R-NO2 “nitro”
How to make alkyl halides (see previous notes & eg)
1) Addition reactions with a halogen (Br2) or hydrogen halide (HCl) and an
alkene or alkyne
2) Substitution reactions with a halogen (Br2) or hydrogen halide (HCl) and
an alkane or aromatic compound
Note - Alkyl halides can undergo “elimination” reactions (reverse addition)
to make alkenes (need basic conditions)
Eg CH2 – CH – CH3 + (OH)-1  CH2 ═ CH – CH3 + H2O + Br -1
H
Br
2-bromopropane
propene
Nitrogen Containing Functional Groups (Sect. 1.7)
Amines – an ammonia molecule (NH3) with 1, 2 or 3 hydrogens replaced by
an alkyl branch(es).
Eg. “A” H2N—CH3 “B”
H —N—CH3
“C” H3C—N—CH3
CH3
1o amine
(R-NH2)
2o amine
(R-N-R1)
CH3
3o amine
( R-N-R1)
R11
H
Nomenclature – prefix “amino” + longest branch, suffix “amine”
- 2o and 3o amines include “N” in prefix to denote branch is on Nitrogen
- list alkyl branches alphabetically if different in length
- two methods used (IUPAC vs suffix method)
Example
“A”
IUPAC name
aminomethane
Suffix name
methylamine
“B”
N-methylaminomethane
dimethylamine
“C”
N,N-dimethylaminomethane
trimethylamine
Practice – draw N-ethylamino-n-propane
Properties
– organic BASES
- unpleasant odours eg. (H2NCH2CH2CH2CH2NH2)
1,4-diaminobutane aka “putrescine”
- polar area, usually water soluble
- important in proteins (“amino acids”) and DNA (nitrogenous base)
- prepared by reaction of ammonia (NH3) with an alkyl halide (R-X)
(see eg p 73)
Nitrogen Compounds “Amides”
R—CO—N—R1
R11
- similar structure to an ESTER with a NITROGEN atom replacing the
oxygen in the chain.
- linkage is called a peptide bond in proteins
- formed by a reversible condensation reaction between an AMINE (1o or 2o)
and a CARBOXYLIC ACID
Properties
- weak bases, low solubility in water (unless small molecule)
- amount of “H bonding” determines mp/state etc.
- can undergo hydrolysis reaction with acid/base catalyst to reform
the amine and carboxylic acid
Nomenclature suffix = “amide”
O
H
CH3C—OH
+
H— N—CH3
H—O
+
1 amine
H
small molecule
(aminomethane)
(water)
o
Carboxylic acid
(ethanoic acid)
H+

Heat
O
CH3—C— N—CH3
H
N-methyl ethanamide  suffix
#C’s in amine
#C’s in carboxylic acid
NOTE – amide nomenclature is not required in this course
Oxygen Containing Functional Groups (Sect 1.4)
Alcohols and ethers are ISOMERS of each other.
Ethers (R-O-R1 , oxygen bonded to 2 carbon chains)
1) alkyl groups may be the same C length (ROR) or different (ROR1)
2) less polar than alcohols and more volatile (lower bp)
3) generally unreactive but good solvents (if liquid at Rm Temp) and
also used as anaesthetics (“diethyl ether”)
4) prepared by condensation reaction of 2 alcohols
Nomenclature – 2 ways used
CH3 – O – CH2CH3
IUPAC methoxyethane
Or methyl ethyl ether (complexity rule used)
Alcohols (R-O-H, “hydroxyl” group)
1) contain the “OH” group that is polar
2) classified as 1o, 2o or 3o based on whether C-OH is attached to H or
other carbons
3) can have more than one hydroxyl group (“polyalcohol” eg sugars)
4) may be found in rings (cyclo, aromatic)
5) used as polar solvents eg ethanol (alcohol) or 2-propanol (rubbing
alcohol) and also as flavourings
6) prepared by addition of water to alkenes (“hydration”) or reduction of
aldehydes, ketones or carboxylic acids)
7) also undergo reactions such as : combustion, dehydration/elimination
to form an alkene, condensation (with c. acids  ester) as well as
oxidation reactions (can make ketones, aldehydes, c. acids)
Nomenclature suffix = “ol”, prefix = “hydroxyl”
Eg. CH3CH2CH2OH = 1-propanol
OH
hydroxybenzene or phenyl alcohol
(phenol)
Carbonyl Functional Groups (O═C
, Sect 1.5)
Def’n – contains a carbon double bonded to an oxygen atom
- may be found on an END carbon (“aldehyde”, RCOH) or
in the middle of the parent chain (“ketone”, RCOR1)
1) the carbonyl group is polar so these compounds are used as solvents
although they have lower boiling points than alcohols (no H bonding)
2) volatile compounds which makes them good chemical “signals” in
nature (“smells”) eg. Pheromones, formaldehyde
3) prepared by the controlled oxidation of alcohols which may be
reversed by a controlled reduction reaction (Bio connection)
Note - [O] = oxidizing agent needed [R] = reducing agent needed
[O]
eg. A) 2- propanol  propanone

[R]
o
“2 alcohol”
ketone
B)
[O]
[O#2]
1-propanol  propanal
 propanoic acid


[R]
[R]
o
“1 alcohol”
aldehyde
carboxylic acid
C) 3o alcohols don’t easily oxidize
[O]
methyl- 2- propanol  no reaction
Nomenclature
O
Aldehydes – suffix = “al
Eg CH3CH2 - C- H
propanal
Ketones – suffix = “one”
O
CH3CH2 – C – CH2CH2CH3
3- hexanone
Functional Groups with 2 Oxygens (Sect. 1.6)
Carboxylic acids – contain the “carboxyl” group (RCOOH)
- weak organic acids (acidic H) found in various foods and
drugs
OH
COOH
eg. CH3COOH
CH3 – CH – COOH
O—C—CH3
O
acetic acid
(ethanoic acid)
lactic acid
(2-hydroxypropanoic acid)
acetylsalicylic acid
(ASA)
Nomenclature – suffix is “oic” acid (highest priority)
Eg. HOCH2CH2CH2COOH
4-hydroxybutanoic acid
Properties – polar molecules, high bp/mp due to H bonds
- acidic properties/reactions (eg. Neutralization)
- formed by the oxidation of an aldehyde
[O]
[O*]
eg CH3CH2OH  CH3COH  CH3COOH
ethanol
“sour tasting wine” =
ethanol
ethanoic acid
alcohol + “air”  vinegar
Reactions
Carboxylic acids undergo CONDENSATION reactions with:
a) alcohols  esters + water “esterification”
b) amines  amides + water
bio = “peptide bonds”
General Reaction
H+
eg. R—O—H + H—O—CO—R1  R—O—CO—R1 + H—O—H
“ester”
Esters – an organic “salt”
RCOOR1 (Sect. 1.6)
-
occur naturally in plants
used as scents (perfume) and flavourings
- polar region (less than carboxylic acids)
- prepared by a reversible condensation reaction (usually an alcohol
and c. acid) with removal of a small molecule such as water
- reaction usually needs an acid catalyst and is sometimes called
“esterfication”
- reverse reactions (“hydrolysis”) need a strong base (NaOH)
eg. saponification (soap making) of a triglyceride or “fat” (Lab 2)
-
Nomenclature - “alcohol” + “c. acid” suffix = “oate”
O
CH3CH2CH2C—OH + H—O—CH2CH3
Carboxylic acid
Alcohol
Butanoic acid
Ethanol
H+

Heat
H— O
+
H
Small molecule
O
CH3CH2CH2C — O—CH2CH3
from acid
from alcohol
ester link/bond
Name = ethyl butanoate  ester suffix
#C’s in carboxylic acid
#C’s in alcohol
Practice – write an esterification reaction for methanol and
2- methylpropanoic acid. Name the ester formed.
(water)