Electrostatic Potential MapsModels that visually portray polarity and dipoles

Hydrogen Halides

When identical polar bonds point in opposite directions,the effects of their polaritiescancel, giving no net dipolemoment. When they do notpoint in opposite directions,there is a net effect and a netmolecular dipole moment,designated δ.

Molecular PolarityMolecular Polarity& Dipole Moment& Dipole Moment The vector sum of the magnitude and the direction of the individual

bond dipole determines the overall dipole moment of a molecule

Molecular Dipole Moment

An electrically charged rod attracts a streamof chloroform buthas no effect on a stream of carbontetrachloride.

Ammonia and in the Ammonium Ion

Water

• Resultant Molecular Dipoles > 0• Solubility: Polar molecules that

dissolve or are dissolved in likemolecules

Polarity & Physical PropertiesOzone and Water

• The Lotus flower• Water & dirt repellancy

0.1278 nm

The “Lotus Effect”Biomimicry

http://bfi.org/biomimicry

• Lotus petals have micrometer-scale roughness, resultingin water contact angles up to 170°

• See the Left image in the illustration on the right.

Wax

The “Lotus Effect”Biomimicry

http://www.sciencemag.org/cgi/content/full/299/5611/1377/DC1

• Isotactic polypropylene (i-PP) melted betweentwo glass slides and subsequent crystallizationprovided a smooth surface. Atomic forcemicroscopy tests indicated that the surface hadroot mean square (rms) roughness of 10 nm.

• A) The water drop on the resulting surface had acontact angle of 104° ± 2

• B) the water drop on a superhydrophobic i-PPcoating surface has a contact angle of 160°.

Science, 299, (2003), pp. 1377-1380, H. Yldrm Erbil, A.Levent Demirel, Yonca Avc, Olcay Mert

Molecular Representations

Empirical Formula, Molecular Formula, Structure:(Lewis, Kekule, Condensed, Line), Visual Model:wireframe, stick, ball & stick, space filling, electrostatic,energy surface

Draw bond-line structures for each of the four molecules.

1.

2.

3.

4.

ketone

O

1.

aldehyde

H

O

O

2.NOT

carboxylic acid

C

O

O

H

C

O

2

H

O

H

O

or

or

3.

ester (carboxylic acid ester)

O

O

C

H

3

O

O

C

O

O

C

H

3

or

NOT

4.

Question 12

• The molecular formula of morpholine is:• A) C2HNO• B) C4HNO• C) C4H4NO• D) C4H5NO• E) C4H9NO

Question 13

• The respective number of bonded pairs ofelectrons and of unshared pairs ofelectrons in morpholine is:

• A) 7, 0• B) 7, 1• C) 15, 0• D) 15, 1• E) 15, 3

Formulas &Kekulé / Condensed / Bond-Line

Structures / Drawings

Molecular formula? Empirical Formula?

Bond-Line Structure?

Question 14

• The bond-line representation for(CH3)2CHCH2CH2CHBrCH3 is

•• A) B)•

• C) D)

Select the best condensed structural formula forthe following bond-line structure:

H

HO OH

O

A. (CH3)2CHCH2COHOHCOHB. CH3CH3CHCH2C(OH)2CHOC. (CH3)2CHCH2C(OH)2CHOD. (CH3)2CHCH2C(OH)2COHE. CH3CHCH3CH2C(OH)2CHO

Question 15

Line Drawing and Ball & Stick

8.16 Å (0.816 nm)

http://chemconnections.org/organic/chem226/Labs/Smell/Smell-Stereochem.html

Question 16While on-line, click on the jmol-structureon the left.Which one of the formulas orstructural renderings thatfollow is correct?

C

H

3

C

H

2

O

H

C

H

2

C

O

O

H

C

H

3

O

O

H

O

H

O

C

2

H

3

O

B)

C)

D)

E)

A)

Question 17

• How many constitutional alcohol isomershave the molecular formula C4H10O?

• A) two• B) three• C) four• D) five

More Molecular Representations

Empirical Formula, Molecular Formula, Structure:(Lewis, Kekule, Condensed, Line), Visual Model:wireframe, stick, ball & stick, space filling,electrostatic, energy surface

Worksheet: Organic Molecules 1http://chemconnections.org/organic/chem226/Labs/VSEPR/

Very Large Molecules:DNAhttp://www.umass.edu/microbio/chime/beta/pe_alpha/atlas/atlas.htm

Views & Algorithms

10.85 Å10.85 Å

Several formats are commonly usedbut all rely on plotting atoms in 3dimensional space; .pdb is one of themost popular.

Very Large Moleculeshttp://info.bio.cmu.edu/courses/03231/ProtStruc/ProtStruc.htm

B-DNA: Size, Shape & Self Assembly

http://molvis.sdsc.edu/pdb/dna_b_form.pdb

46 Å

12 base sequence

(1953-2003)

Rosalind Franklin’sPhoto

Atomic Orbitalss and p orbitals

Molecular Orbitals

• Atomic orbitals mix to form molecular orbitals

•The total number of molecular orbitals(bonding + non- and anti bonding orbitals)equal the total number of atomic orbitals

• Α σ bond is formed by overlapping of two sorbitals

In-phase overlap of s atomic orbitals forma bonding MO (no node);

Out-of-phase overlap forms an antibonding MO (has node)

A single bond is a σ bond with a bond order of 1.

A sigma bond (σ) is also formed by end-on overlapof two p orbitals

Double bonds have 1 σ and 1 π bond with a bond order of 2.A π bond is weaker than a σ bond.A double bond is shorter and stronger than a single bond.

Pi bond (π) is formed by sideways overlap of two parallel p orbitals Mixing Atomic Orbitals

Hybridization of s and p orbitals

Single Bonds (Methane)

Hybridization of s and p atomic orbitals:

http://chemconnections.org/organic/Movies%20Org%20Flash/HybridizationofCarbon.swf

The atomic orbitals used in bond formationdetermine the bond angles

• Tetrahedral bond angle: 109.5°

• Electron pairs spread themselves into space as far from each other as possible

Hybrid Orbitals of EthaneBonding in Ethene: A Double Bond

Double bonds have 1 π and 1 σ bond.A double bond is shorter and stronger than a single bond.

http://chemconnections.org/organic/Movies%20Org%20Flash/HybridizationofCarbon.swf

• The bond angle in the sp2 carbon is 120°

• The sp2 carbon is the trigonal planar carbon

An sp2-Hybridized Carbon

http://chemconnections.org/organic/Movies%20Org%20Flash/HybridizationofCarbon.swf

Ethyne: A Triple Bondsp-Hybridized Carbon

• A triple bond consists of one σ bond and two π bondswith a bond order of 3.•Triple bonds are shorter and stronger than double bonds• There is a bond angle of the sp carbon: 180°

Question 18

• What is the molecular shape of each of thecarbons of tetrachloro ethene (Cl2C=CCl2)?

• A) tetrahedral• B) bent• C) trigonal planar• D) linear• E) trigonal pyramidal

http://chemconnections.org//organic/Movies Org Flash/hybridization.swf

Summary• A π bond is weaker than a σ bond

• The greater the electron density in the region of orbital overlap, the stronger is the bond• The more s character, the shorter and stronger is the bond• The more s character, the larger is the bond angle

Reactive IntermediatesCarbocation

Reactive IntermediatesRadical

Reactive IntermediatesCarbanion