Ch 10 - 11

Organic Chemistry

Section 10-1

• The Study of Compounds of Carbon

• “Organic Chemistry” • Well over 100,000 new every year

• Compounds chiefly of (C, H, O, & N)

• Original misconceptions – That only living organisms could “produce” organic

compounds

– 1st to disprove? Friedrich Wohler (1800-1882)

– Ammonium chloride + Silver cyanate

– Produced UREA!

– 1st Synthetic production of an organic compound

Section 10-2 Sources of Organic Compounds

• Nature

• Laboratory Synthesis

• Synthetic Compounds are identical to compounds from their natural source

• Vitamin C from tablet

• Vitamin C from fruit

• Same Exact Compound

Section 10-3

• Lewis model of bonding: primary patterns • CARBON: 4 bonding sites

• NITROGEN: 3 bonding sites (1 unshared pair)

• OXYGEN: 2 bonding sites (2 unshared pairs)

• HYDROGEN: 1 bonding site

• HALOGENS: 1 bonding site (3 unshared pairs)

Section 10-3

Bond angles & Shape:

• Primary shape patterns around central carbon atoms

• Only Single Bonds: bond angle = 109.5⁰

• 1 Double Bond: bond angle = ~120⁰

• 2 Double or 1 Triple Bond: bond angle = 180⁰

Table 10.1 Lewis Structures & Shapes

• Ethane (C2H6) • Ethylene (C2H4) • Acetylene (C2H2) • Ethyl chloride (C2H5Cl) • Methanol (CH3OH) • Formaldehyde (CH2O) • Methylamine (CH3NH2) • Methyleneamine (CH2NH) • Hydrogen cyanide (HCN)

Condensed Structural Formulas

• Combination of a molecular formula and a Lewis Structure.

• CARBON-CARBON & CARBON-HYDROGEN bonds are “assumed”

CH3 CH2 CH

• Examples: CH3CH2CH2CH3 CH3CHCHCH3

Structural Formula to Lewis Structure Lewis Structure to Shape – Bond angle

• Examples: • Acetic acid (CH3COOH)

• Ethylamine (CH3CH2NH2)

• Students: • Ethanol (CH3CH2OH)

• Propene (CH3CHCH2)

Section 10-4 Functional Groups

• Groups of O, N, H, and/or S attached to CARBON

• Sites of Chemical Reactions

• Used to divide organic compounds into CLASSES

• Used for NAMING organic compounds

Functional Group Alcohols

• -OH “hydroxyl group”

Functional Group Ethanol

• Primary (1⁰), Secondary (2⁰), Tertiary (3⁰) alcohols depend on the number of carbon atoms bonded to the carbon bearing the –OH group.

1⁰ alcohol 2⁰ alcohol 3⁰ alcohol

• Draw the Lewis structure and condensed formulas for the two alcohols of molecular formula C3H8O. Classify each as primary, secondary, or tertiary.

• Draw the Lewis structures and condensed formulas for the four alcohols of C4H10O. Classify each.

Functional Group Amines

• N bonded to 1, 2, or 3 CARBONS: “amino group”

• Primary: N bonded to one C

• Secondary: N bonded to two C’s

• Tertiary: N bonded to three C’s

methyl amine dimethyl amine trimethyl amine

1⁰ 2⁰ 3⁰

• Draw the condensed structural formulas for the two primary amines of C3H9N

• Draw the condensed structural formulas for the three secondary amines of C4H11N

Functional Group Aldehydes

• - C=O “carbonyl group”

• H and C and/or H complete the C bonded to the “carbonyl”

• Written: - CH=O or – CHO

Functional Group Acetaldehyde

• Draw the condensed formulas for the two aldehydes of C4H8O

Functional Group Ketones

• -C=O “carbonyl group”

• Carbon of “carbonyl” is attached to 2 other carbons.

• Written ? - C=O

Functional Group Acetone

• Draw the condensed formula for three ketones of C5H10O

Functional Group Carboxylic Acids

• COOH “carbonyl + hydroxyl”

• Also written: - CO2H

Functional Group Acetic Acid

• Draw the condensed formula for the single carboxylic acid of C3H6O2

ADD THIS ONE: Nitro’s

• -NO2 groups

• nitroglycerine

Section 11-1 • Hydrocarbons

• Compounds consisting of only hydrogen and carbon

• Saturated Hydrocarbons • Contain only single bonds

• Carbon has the MAXIMUM bonding

• Greatest # of Hydrogen bonded to carbons

• Aliphatic: Long chain molecules » Aleiphar: Greek for Fat or Oil

• Alkanes • Saturated hydrocarbons arranged in an open chain

• Cycloalkanes • Saturated hydrocarbons where the chain is bonded to form a

ring

Section 11-2 Alkane Structure

• 1st Ten Alkanes with un-branched chains (page 266, table 11.1)

• Must know names, molecular formulas and condensed structural formulas

» Methane 1 C CH4

» Ethane 2 C CH3CH3

» Propane 3 C CH3CH2CH3

» Butane 4 C CH3CH2CH2CH3

» Pentane 5 C CH3CH2CH2CH2CH3

» Hexane 6 C CH3CH2CH2CH2CH2CH3

» Heptane 7 C CH3CH2CH2CH2CH2CH2CH3

» Octane 8 C

» Nonane 9 C

» Decane 10 C

Section 11-3 Isomerism

• Constitutional Isomers: • Compounds that have the same molecular formula but

different structural formulas

• Literally different compounds

• Unique physical and chemical properties

• Examples • Butane (C4H10): CH3CH2CH2CH3

» Boiling point: -0.5⁰C

• 2-methylpropane: CH3CHCH3CH3 (need to draw!) » Boiling point: -11.6⁰C

• Ex 11.1 – Same compound or constitutional isomers?

• Find the longest continuous chain

• Start counting from the end with the closest branch

• Compare length of chains and location of branches

• Draw the constitutional isomers of C5H12 (3)

• Draw the constitutional isomers of C6H14 (5)

Section 11-4 Nomenclature of Alkanes

• Naming system

• IUPAC: International Union of Pure and Applied Chemistry

• Rule Overview: • Longest Un-branched chain

» Use a prefix to indicate number of carbons in chain

» Add the suffix “ane” to show saturated hydrocarbons

• Branched Parts (Substituents) » Use prefix for size

» Add suffix “yl” to indicate a branch

Table 11.3 Common prefixes

• meth - 1

• eth - 2

• prop - 3

• but - 4

• pent - 5

• hex - 6

• hept - 7

• oct - 8

• non - 9

• dec - 10

• Other prefixes • iso

– chain that ends in CH(CH3)2

– will be a symmetrical branched chain

• sec – – “secondary”

• tert – – “tertiary”

CH3

CH3

CH3

CH3

CH3

CH3CH3

CH3

CH3

CH3

Table 11.4 Common alkyl groups

• methyl

• ethyl

• propyl

• isopropyl

• butyl

• isobutyl

• sec-butyl

• tert-butyl

CH3CH3

Condensed Structural Condensed Structural Name

CH3CH2CH2CH2CH2CH2CH2CH3

CH3CH2CH2CH2CH2CH2CH2CH3

CH3CH2CH2CH2CH2CH2CH2CH3

CH3CH2CH2CH2CH2CH2CH2CH3

CH3CH3

CH3

CH3CH3

CH3

CH3CH3

CH3

Naming Vocabulary

• Parent Chain

Longest Chain

• Substituent

Branch

Be Careful!

CH3CH3

CH3

CH3CH3

CH3

Rules for Naming Alkanes Examples

1) Name the longest continuous chain using a prefix to indicate the number of carbons with suffix “ane”.

2) If branched, the longest chain is the parent chain, and its name becomes the root name.

3) Each branch is given a name and number.

4) If there is one substituent (branch), number the parent chain for the end that gives the branch the lowest number.

5) If the same substituent (branch) occurs more than once, number the parent chain from the end that gives the lowest number to the branch encountered first. Use di, tri, tetra. prefixes for the substituent.

6) If there are two or more different substituents (branches), list them in alphabetical order and number the chain that gives the lowest # to the first encountered branch. If there are different branches on the same opposite ends of the parent chain, the branch with the lower alpha order is given the lower number.

7) Prefixes – di,tri,tetra…..are not included in the alphabetizing. Neither are sec and tert. Names of substituents are alphabetized first and then the prefixes are inserted.

• Name the following Alkanes

Common Names

• Many of the abundant carbon compounds also have “common” names from previous naming systems and common culture.

• We will concentrate on IUPAC names vs. the common name

• Exception: When naming a SUBSTITUENT

• Example: • Butane

• Methyl propane (isobutane)

11-5 Cycloalkanes

• Cyclohydrocarbons

– Also known as cyclic hydrocarbons

– Carbons are joined to form a ring

– 3-30 carbon rings are found in nature

– 5 & 6 carbon rings are especially abundant

– Represented by a regular polygon

– Often drawn without Carbon & Hydrogen

– Named using prefix “cyclo” along with the parent chain prefix

cyclopentane

• Condensed structural formula

• Line angle drawing

Draw the following cycloalkanes

• isopropyl cyclopentane

• 1-tert-butyl 4-methyl cyclohexane

• isobutyl cyclopentane

• sec-butyl cycloheptane

• 1-ethyl 1-methyl cyclopropane

11-7 Shapes of alkanes & cycloalkanes

• Alkanes – Conformations

• 3-d shapes a molecule can have • single bonds have free rotation • Example – Butane fig. 11.3 pg 277

• Cycloalkanes – Cyclopentane

• Most stable conformation: envelope fig. 11.4

– Cyclohexane • Most stable conformation: chair fig. 11.6 • Axial bonds

– Parallel to center axis line – 3 up, 3 down

• Equatorial bonds – Perpendicular (approximately) to center axis line – 6 total

Axial vs. Equatorial

• Methylcyclohexane: 2 Conformations fig 11.7

11-8 cis –trans Isomerism in Cycloalkanes

• Have the same molecular formula

• Have the same attachments of substituents

• Have different shapes because of the restricted movement around C-C bonds in a ring (NO FREE ROTATION!)

• Called: Stereoisomers • Same structure and formula, but different orientation

within the molecule

• cis: “same side” • cis-1,2-dimethylcyclopentane

• 2 drawing methods

• trans: “across” • trans-1,2-dimethylcyclopentane

• 2 drawing methods

• Example 11.7:

– Which structures show cis or trans isomerism?

11-9 Physical properties of alkanes

• Melting Point and Boiling Point

• Increase as molecular weight increases

• Decrease with branching (less surface area)

• Solubility

• All are insoluble in water!

• Density

• All are LESS dense than water!

11-10 Alkane Reactions

• Un-reactive except for oxidation • ONLY COMBUSTION!

11-11 Alkane Sources

• Natural Gas & Crude Oil • Separation Techniques FRACTIONAL DISTILLATION

• Octane rating NOT WHAT YOU WOULD THINK

• Octane Rating – Gasoline is made of a mixture of C6 to C12

hydrocarbons:

– Some explode prematurely when combusted in an engines cylinder KNOCK!

– 2 representative molecules • isooctane (2,2,4-trimethylpentane): Very little KNOCK

• heptane: More KNOCK

– Octane Rating represents the characteristics of the mixture compared to these (% isooctane)

– Octane itself is a very HIGH KNOCK compound and is -20 on the rating scale