organic chemistry carbon-containing compounds and their properties

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


• 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




H3CCH2CH2OH

HOH(H2O) involved in dehydrations




OH involved in additions

H3CCH2CH2OH




* * H3CCH2CH2OH + [O]xidizer

H3CCHC=O + H2[O]xidizerH




HOH(H2O) involved in dehydrations

* * H3CCH2CH2OH + catalyst

H3CCH2=CH2

Example Reactions -- Alcohols• –OH is site of reactivity


An ester. Reaction is reversible.

O* *H3CCH2CH2OH + CH3C

H3CCH2–CH2–O–CCH3 + H2O

O–H

=

–=O


• Oxidation of alcohol in Citric acid Cycle

HO2CCH2CCO2H + [O]

HO2CCH2CCO2H + H2[O]

H

OH=

O

“Malate” to “Oxaloacetate”


• 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


CH2–O–C–R=

O

CH–O–C–R'

=O

CH2–O–C–R"

=

O

Gly

cero

l “ba

ckbo

ne”

“Fatty acid” fragments


CH2–O–C–R=

O

CH–O–C–R'

=

O

CH2–O–C–R"

=

O+ H2O (& enzymes)


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

organic chemistry carbon-containing compounds and their properties

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