organic chemistry carbon-containing compounds and their properties
TRANSCRIPT
Organic Chemistry
Carbon-containing Compounds and their Properties
Organic Compounds
• Contain carbon atoms, often several per molecule
• Possibly derived from living sources
• About 90% of the known substances are organic. Most of these contain only a few kinds of elements: C, H, O, N, S
• Most intramolecular bonding is covalent
Organic Compounds
• Many organic substances are flammable
• Frequently, more than one substance of same overall formula – isomers
• Important biomolecules are organic
– lipids, carbohydrates, proteins, hormones, nucleic acids, etc
Flammable
C,H + O2 CO2 + H2O + energy
Since organic substances contain C (and almost always H), combustion occurs forming CO2 and water
Isomers–Example:C3H8O
H3CCH2CH2OH
H3CCHCH3
OH
H3COCH2CH3
bp=97°C
bp=82°C
bp=8°C
Organic Families
• Millions of organic compounds exists
• Grouped in families to correlate similar properties and to predict chemical and physical behaviors
• Families are based on similar molecular structures, especially similar functional groups
Organic Families
• Functional groups– Sub-molecular units that are responsible for particular
chemical and physical properties– May be single atoms; often are several atoms joined
together– Molecules may contain several functional groups (or
none)
• Chemical Reactions often occur (or can be “designed”) that affect only certain functional groups, leaving much of molecular structure unaffected
Organic Families
• Molecules containing only C and H atoms with only single bonds are considered to have no functional group– Alkanes, a type of hydrocarbon– Still, these molecules can react; they undergo
oxidation, or combustion, for example
Alkanes
C HH
H
H Methane, the simplest of alkane;meth–from “wood,” as in “wood alcohol,”
or methanol, containing one carbon atom per molecule
CCHH
H
H
H
H Ethane, the two-carbon alkane;eth–from “ether”; the ether of anesthesia
is made from two-carbon molecules
Alkanes
C HH
H
H
CCHH
H
H
H
HOr, C2H6,
Also, CH4
or, CH3CH3
Methane
Ethane
Alkanes
Propane, the three-carbon alkane;pro–from “first” or “propanoic acid,”
simplest 3-carbon fatty acid
CCCHH
H
H
H
H
H
H
CCCCHH
H
H
H
H
H
H
H
H Butane, the four-carbon alkane;but–from“butter”; butyric acid,
containing 4 carbons and named for butter, forms as butter sours
Alkanes
Or, C3H8, or CH3CH2CH3CCCHH
H
H
H
H
H
H
CCCCHH
H
H
H
H
H
H
H
HC4H10
CH3CH2CH2CH3
Propane
Butane
Alkanes
Pentane, the five-carbon alkane;pent–for “five” as in “pentagon”
CCCCCHH
H
H
H
H
H
H
H
H
H
H C5H12
CH3CH2CH2CH2CH3
Alkanes
Octane, the 8-carbon alkane;oct–for “eight” as in “octet” or “octagon”
H
C8H18 CH3CH2CH2CH2CH2CH2CH2CH3
CCCCCCCCHH
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
Alkanes
Methylpropane,H3CCCH3
CH3
H
CH
H
HOr CH3 or
CH3
=“methyl,” an alkyl group
Alkanes
H3CCCH2CH3
CH3
CH3
2,2-dimethylbutane
2,2-dimethylbutaneH3CCH2CCH3
CH3
CH3
Alkanes
H3CCHCH2CH2CH3
CH3
CH2CH3
3-ethyl-2-methylpentane
Alkanes
H2C CH2
CH2H2C
CH2
Cyclopentane =
CH3
CH3
CH3
1,1,3-trimethylcyclohexane
Alkenes
Ethene, the simplest of alkenes
Propene, the three-carbon alkene
Contain one or more C=C double bonds
C=CHH
HH
CH
H
H
C=CHH
H
H2C=CH2
CH3CH=CH2
Alkenes
1-Butene
trans-2-Pentene
Contain one or more C=C double bonds
CH3CH2CH=CH2
H2C=CHCH2CH3 1-Butene
C=CCH2CH3H
HCH3
C=CCH2CH3
H H
CH3
cis-2-Pentene
Alkynes
1-Butyne
4-Methyl-2-pentyne
Contain one or more CC triple bonds
CH3CH2CCH
HCCCH2CH3 1-Butyne
CH3CCCHCH
3
CH3
1 2 3 4 5
AlcoholsContain –OH functional group
2-Propanol,H3CCCH3
OH
H
= “OH,” an alcohol group
CH3CH2CCH2CH3
CH3
OH 3-Methyl-3-pentanol
Aldehydes and KetonesContain C=O functional group
Propanal, an aldehyde
=“CHO,”an aldehyde group
3-Pentanone, a ketone
CH3CH2CO
H
=
CH3CH2CCH2CH3
O
=
Similar to aldehyde but not at end of molecule
Aldehydes and KetonesContain C=O functional group
=
O
Cyclohexanone
HCC-CH2-C-CH3
=
O4-Pentyn-2-one
(also, alkyne-like)
Physical Properties
• Such as –– Boiling point, melting point– Usual state of matter (solid, liquid, gas)?– Solubility characteristics
• Relate to and Predictable from Molecular Structure
Boiling Point
• Temperature where liquid begins to evaporate rapidly (bubbles readily form in liquid)
• Higher bp for larger molecules
• Very large molecules usually result in solid material
Boiling Point
• FW<60 g/mol: usually gases
• FW between 60 and 300: liquids
• FW>300: solids
C4H10, bp = -0.5°C (FW = 58)
C8H17Br, bp = 200°C (FW = 193)
C20H42, mp = 37°C (FW = 283)
Boiling, Melting Points
• Shape influences
• More compact, symmetrical molecules have lower bp but higher mp
CCCCCHH
H
H
H
H
H
H
H
H
H
H
H3CCCH3
CH3
CH3
bp = 36°C,mp = -130°C
bp = 10°C,mp = -17°C
Both have FW = 72, C5H12
Boiling Point• H-Bonding increases bp
• Especially noticeable for smaller molecules
H2O, bp = 100°C (FW = 18, H-bonded)
O2, bp = -183°C (FW = 32, no H-bonding)
C2H5OH, bp = 78°C (FW = 46, H-bonded)
C2H5F, bp = -32°C (FW = 48, no H-bonding)
Organic Chemical Reactions
• Types of changes usually predictable by the functional group(s) present in the molecules
• Often, reactions can be “directed” to occur to specific functional groups, even when several groups are present
• Biological reactions almost always catalyzed by enzymes
Example Reactions -- Alkanes
• Least reactive of all families
• Combustion and other oxidations are typical reactions
C3H8 + 5 O2 3 CO2+ 4 H2O
CH4 + Cl2 CH3Cl + HCl
Example Reactions -- Alkenes
• Many reactions change C=C to C–C
• Additions
C=C
H H
CH3H3C
+ H2 CH3–CH2–CH2–CH3
Example Reactions -- Alkenes
• Many reactions change C=C to C–C
• Some reactions affect C–H adjacent to double bond -- substitutions
C=C
H H
CH3H3C h + Br2 C=C
H H
CH2BrH3C+ HBr
Example Reactions -- Alcohols
• –OH is site of reactivity
• Oxidations, dehydrations, additions are common
H’s involved in oxidation
H3CCH2CH2OH
Example Reactions -- Alcohols
• –OH is site of reactivity
• Oxidations, dehydrations, additions are common
H3CCH2CH2OH
HOH(H2O) involved in dehydrations
Example Reactions -- Alcohols
• –OH is site of reactivity
• Oxidations, dehydrations, additions are common
OH involved in additions
H3CCH2CH2OH
Example Reactions -- Alcohols
• –OH is site of reactivity
• Oxidations, dehydrations, additions are common
* * H3CCH2CH2OH + [O]xidizer
H3CCHC=O + H2[O]xidizerH
Example Reactions -- Alcohols
• –OH is site of reactivity
• Oxidations, dehydrations, additions are common
HOH(H2O) involved in dehydrations
* * H3CCH2CH2OH + catalyst
H3CCH2=CH2
Example Reactions -- Alcohols• –OH is site of reactivity
• Oxidations, dehydrations, additions are common
An ester. Reaction is reversible.
O* *H3CCH2CH2OH + CH3C
H3CCH2–CH2–O–CCH3 + H2O
O–H
=
–=O
Example Reactions -- Alcohols
• Oxidation of alcohol in Citric acid Cycle
HO2CCH2CCO2H + [O]
HO2CCH2CCO2H + H2[O]
H
OH=
O
“Malate” to “Oxaloacetate”
Example Reactions -- Alkenes
• Addition in Citric acid Cycle
HO2CCH=CHCO2H + H2O
“Fumarate”to“Malate”
HO2CCHCHCO2HOH
H
Amines
• Contain nitrogen, N
• Are usually basic, similar to ammonia, NH3
• React with acids
CH3NH2
methylamine
(CH3CH2)2NHN,N-diethyl amine
Amines
• React with organic acids to form amides• Reactions occur indirectly or by means of enzymes
OH3CCH2CH2NH2 + CH3C
H3CCH2–CH2–N–CCH3 + H2O
O–H
=
–=O
HAn amide; also, called peptide in biological systems
Proteins• Polymeric amides, or “polypeptides”
• Formed from amino acidsO
CCHNH2O–H
=–
R O
CCHNH2O–H
=–
R'
+ H2O
+
A dipeptide
O
CCHNO–H=–
R O
CCHNH2
=
R'
H
R and R' contain H and often C, N, O, and/or S
Proteins
A tridecapeptide (13 amino acid units)
H2N–CH–CO–NH–CH–CO–NH–CH–CO–NH–CH–CO
R1 R2 R3 R2N
H–C
H–C
O–N
H– C
H– C
OR
4R
4–NH
–CO
–CH
R2
NH–CO–CH–NH–CO–CH–NH–CO–CH–NH–
R3 R4 R1
R2
CH–CO–NH–CH–CO–NH–CH–CO2H
R3 R3
Esters
• Can be formed from acids and alcohols
• Provide many natural fruit flavors and essences
• Basis of simple fats, or triglycerides
R–OH +
O
CCH2R'O–H
=–R–O2C–CH2–R' + H2O
An ester
Simple Fats -- Triglycerides
CH2–O–C–R=
O
CH–O–C–R'
=O
CH2–O–C–R"
=
O
Simple Fats -- Triglycerides
CH2–O–C–R=
O
CH–O–C–R'
=O
CH2–O–C–R"
=
O
Gly
cero
l “ba
ckbo
ne”
“Fatty acid” fragments
Simple Fats -- Triglycerides
CH2–O–C–R=
O
CH–O–C–R'
=
O
CH2–O–C–R"
=
O+ H2O (& enzymes)
Simple Fats -- Triglycerides
CH2–O–C–R=
O
CH–O–C–R'
=
O
CH2–O–C–R"
=
O+ H2O (& enzymes)
CH2OH
CHOH
CH2OH
+
RCO2H
R'CO2H
R "CO2H
Fatty acids
Glycerol
Carbohydrates• Generally have formula equivalent to
Cx(H2O)y
– C6H12O6
– C12H22O11
– Etc
• Also called saccharides or sugars
• Simple or complex– Simple sugars
– Starches and glycogens
Carbohydrates
-D-glucose, C6H12O6CH2
OH
OH
OH
OH
H
H
H
H
CHO
OHD-glucose, C6H12O6
OH
H
OHH
OH HOH
H
OH
OH
Carbohydrates
OH
H
OHH
OH HOH
H
OH
OH
-D-glucose, C6H12O6CH2
OH
OH
OH
OH
H
H
H
H
CHO
OHD-glucose, C6H12O6
1
23
4
5
6
1
2
3
4
5
6
Carbohydrates
OH
H
OHH
OH HOH
H
OH
OH
-D-glucose, C6H12O6
OH
H
OHH
OH HOH
H
OH
OH
Remove H2O
Carbohydrates
OH
H
O
H
OH HOH
H
OH
OH
OH
H
OHH
OH H
H
OH
OH
-Maltose, C12H22O11
Carbohydrates
OH
H
O
H
OH HOH
H
OH
OH
OH
H
OHH
OH H
H
OH
OH
-Maltose, C12H22O11
Glu1 4Glu1
O
Carbohydrates
O
OO
HH
OHH
OH H
H
OH
OH OH
OH
OH
H
OHH
Sucrose, C12H22O11
Carbohydrates
4Glu1 4Glu1
O O4Glu1
O4Glu1 4Glu1
O4Glu1
O etcetc
Amylose, or simple starch4,1--linked glucose units
Carbohydrates
4Glu1
O O4Glu1 4Glu1
O4Glu1
O etc
etc
Glycogen , a starch; cross-linked glucose (also, amylopectin)
O4Glu15
4Glu1
O O4Glu1 4Glu1
O4Glu1
O
4Glu1
O
O4Glu1 4Glu1
O4Glu1
O
5
O4Glu1 4Glu1
O4Glu1
etc
etc
Carbohydrates
4Glu1
4Glu1
O4Glu1
O4Glu1
etc
etc
Cellulose, a plant starch4,1--linked glucose units
O
Carbohydrates
4Glu1
O
4Glu1
O
etcetc
Cellulose, a plant starch4,1--linked glucose units
O
4Glu1
1ulG4O
O
1ulG4 1ulG4