Electrostatic Potential Maps Hydrogen Ha ... Electrostatic Potential Maps Models that visually...

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Transcript of Electrostatic Potential Maps Hydrogen Ha ... Electrostatic Potential Maps Models that visually...

  • Electrostatic Potential Maps Models that visually portray polarity and dipoles

    Hydrogen Halides

    When identical polar bonds point in opposite directions, the effects of their polarities cancel, giving no net dipole moment. When they do not point in opposite directions, there is a net effect and a net molecular 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 stream of chloroform but has no effect on a stream of carbon tetrachloride.

    Ammonia and in the Ammonium Ion

  • Water

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

    dissolve or are dissolved in like molecules

    Polarity & Physical Properties Ozone 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, resulting in 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 between two glass slides and subsequent crystallization provided a smooth surface. Atomic force microscopy tests indicated that the surface had root mean square (rms) roughness of 10 nm.

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

    • B) the water drop on a superhydrophobic i-PP coating 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 of electrons and of unshared pairs of electrons 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 for the following bond-line structure:

    H

    HO OH

    O

    A. (CH3)2CHCH2COHOHCOH B. CH3CH3CHCH2C(OH)2CHO C. (CH3)2CHCH2C(OH)2CHO D. (CH3)2CHCH2C(OH)2COH E. 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 16 While on-line, click on the jmol-structure on the left. Which one of the formulas or structural renderings that follow 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 isomers have 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 1 http://chemconnections.org/organic/chem226/Labs/VSEPR/

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

    Views & Algorithms

    10.85 Å 10.85 Å

    Several formats are commonly used but all rely on plotting atoms in 3 dimensional space; .pdb is one of the most popular.

  • Very Large Molecules http://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’s Photo

    Atomic Orbitals s 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 s orbitals

    In-phase overlap of s atomic orbitals form a 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 overlap of 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 formation determine the bond angles

    • Tetrahedral bond angle: 109.5°

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

    Hybrid Orbitals of Ethane Bonding 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 Bond sp-Hybridized Carbon

    • A triple bond consists of one σ bond and two π bonds with 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 the carbons 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 Intermediates Carbocation

  • Reactive Intermediates Radical

    Reactive Intermediates Carbanion