Embed Size (px)
Citation preview
The Microscale Universe:
Atoms and Molecules
Star: massive gaseous body in outer space (ex. Sun); generates energy through nuclear fusion and emits visible light; Nuclear energy, from the rearrangement of protons and neutrons, power the star and given “birth” to the elements
stars ~ 109 m
Putting Atoms in various arrangement (making Molecules): Preparative Chemistry
Dmitri Mendeleev, father of the Periodic
Table, 1869
A Defining Feature of Chemistry: the ability to create something new
Periodic Table of Elements (Atoms): The Ultimate Lego Set
Inside of the AtomCovalent: share e-
Ionic: transfer e-
Activity:Activity: Atoms vs. Legos Atoms vs. Legos
Legos Grains of Sand
H2O molecules
Sense of Scale:
Atoms are Significantly Smaller
Atomic Architectures are Functional
Taxol: Anticancer Drug
# 100 ~ 4 minutes
# 106 ~ 23 days
# 1026 ~ 1019 years
Periodic Table of Elements (Atoms): The Ultimate Lego Set
?
Hindenburg disaster, 1937
Although we now know that his hypothesis was correct, van’t Hoff has received harsh criticism from renowned chemist and editor of Journal of Practical Chemistry, Adolph Kolbe. Here is an excerpt of his criticism:
“A Dr. H. van ’t Hoff of the Veterinary School at Utrecht has no liking, apparently, for exact chemical investigation. He has considered it more comfortable to mount Pegasus (apparently borrowed from the Veterinary School) and to proclaim in his “The arrangement of atoms in Space” how the atoms appear to him to be arranged in space, when he is on the chemical Mt. Parnassus which he has reached by bold flight.”
Although we now know that his hypothesis was correct, van’t Hoff has received harsh criticism from renowned chemist and editor of Journal of Practical Chemistry, Adolph Kolbe. Here is an excerpt of his criticism:
“A Dr. H. van ’t Hoff of the Veterinary School at Utrecht has no liking, apparently, for exact chemical investigation. He has considered it more comfortable to mount Pegasus (apparently borrowed from the Veterinary School) and to proclaim in his “The arrangement of atoms in Space” how the atoms appear to him to be arranged in space, when he is on the chemical Mt. Parnassus which he has reached by bold flight.”
methane
Polypropylene
Symmetry & Arrangement of atoms in space mattersSymmetry & Arrangement of atoms in space matters
M.P. = 130 ° C
Atactic
Isotactic
Syndiotactic
M.P. = 160 °C
M.P. < 0 ° C
melting points
Working with models allows us to predict physical properties of materials
The strands of syndiotactic pack the closest (intercalated packing), followed by isotactic and then atactic. Syndiotactic would be harder and more plasticky then isotactic
and especially then atactic. Symmetry arrangement of atoms and consequent packing of atomic chains explains why: syndiotactic has higher melting temperature (Tm=160ºC) than isotactic (Tm= 130 ºC), which then has a higher melting temperature than atactic (Tm <0 ºC).
Atactic Isotactic Syndiotactic
The Unifying PrincipleThe Unifying Principle
ZZ
AA
Symmetry and Asymmetry: Symmetry and Asymmetry: on a Microscopic Scale on a Microscopic Scale
Symmetry and Asymmetry: Symmetry and Asymmetry: on a Microscopic Scale on a Microscopic Scale
Assembly of atoms into Symmetric & Asymmetric molecular architectures
& consequences of molecular asymmetry.
Carbon with 4 different atoms bond to it creates an Asymmetric Molecule (Chiral Molecule)
Enantiomers non-superimposable mirror images
(R), D
(S), L
Chiral Molecules Chiral Molecules rotate plane polarized light rotate plane polarized light
Demonstration: Building a simple polarimeter
light sourcelight source
2 polarizers2 polarizers
cupcup
NaOClNaOCl33 crystals crystals
material:material:
demystifying the instrumentdemystifying the instrument
Demonstration: Building a simple polarimeter
The binding specificity of a chiral The binding specificity of a chiral receptor site for a chiral molecule is receptor site for a chiral molecule is
usually only favorable in one wayusually only favorable in one way
(S)-(–)-limonene smells like turpentine (pine)
(R)-(+)-limonene has the odor of oranges
limonenelimonene
*
Chirality: Chirality: Smells Differently in the MirrorSmells Differently in the Mirror
2-methylbutanoic acid acid
R-(‒)Cheesy Sweaty Smell
S-(+)Fruity
Sweet Smell
*
(S)-(+)-carvone smells like caraway
(R)-(–)-carvone smells like spearmint
carvone
* * *
Chirality Governs Drug Action ?Chirality Governs Drug Action ? When chiral compounds are introduced into the body, physiological processes show a high degree of chiral distinction;
Essential physiological process are homochiral;
Biomolecules are made of units Biomolecules are made of units that have the same sense of that have the same sense of chirality:chirality:
PROTEINS PROTEINS L-centered amino acids
NUCLEIC ACIDS (DNA & RNA)NUCLEIC ACIDS (DNA & RNA)D-centered sugar unitsright/left handed helical twist
left-handed DNA (atypical)
Thalidomide horror, late 1950s
Thalidomide, a drug once used to suppress morning sickness
(R) vs. (S)
(S)
Friedman, L.. et al. Science. 1971, 172(3987), 1044-1046.Friedman, L.. et al. Science. 1971, 172(3987), 1044-1046.thalidomidethalidomide
*
Influence of Chirality on Influence of Chirality on Drug ActionDrug Action
Chirality Matters !!!Chirality Matters !!!
Illegal as the Mirror-image formIllegal as the Mirror-image form
non-stimulant
Methamphetamine
stimulant
* *
Influence of Chirality on Influence of Chirality on Drug ActionDrug Action
We have something to eagerly look forward to: Perhaps the answer to the questions regarding the origin of molecular asymmetry on Earth will come in year 2014 ! This is when the robotic lander Philae will detach itself from the orbiter of the Rosetta space craft and land on the comet 67P/Churyumov-Gerasimenko.
a) The Origin of Symmetry & Asymmetry on a Microscopic
(Molecular) ScaleMurchison meteorite, which fell about 60 miles north of Adelaide, Australia in
1969.
One of the first reports stated that the amino acids that were found were equally right and left handed.
Subsequent reports have been controversial…
b) from Microscopic to Macroscopic Scale, Asymmetry Prevails
In 1857, Pasteur has noticed that molds had grown in a dish containing an optically inactive solution, one that did not rotate plane polarized light. Instead of simply throwing away the "contaminated" solution, having curious nature he checked its effect on a light beam. The contaminated solution rotated light!
Pasteur viewed handedness as one of the clearest distinctions between living and dead matter and ultimately proclaimed it to be a profound fact of nature that went far beyond the chemistry of life. He wrote the following: "Life as manifested to us is a function of the asymmetry of the universe
and of the consequences of this fact." later, before the French Academy of Sciences, he made the grand conjecture, "L'univers est dissymetrique."
c) Symmetry & Asymmetry in Living
Organisms
Symmetry & Asymmetry the parallel between Science & ArtSymmetry & Asymmetry the parallel between Science & Art
Artwork of M. C. Escher
Eric J. Heller Gallery
Where science inspires art and art informs science...While a sidelight, Heller said his artwork serves an important
purpose. It doesn't just educate the public about physics, it engages them and interests them in what's going on at the atomic level.
Eric J. Heller Gallery
Where science inspires art and art informs science...While a sidelight, Heller said his artwork serves an important
purpose. It doesn't just educate the public about physics, it engages them and interests them in what's going on at the atomic level.
Drawing Hands, 1948 Still Life with Spherical Mirror, 1934Balcony, 1945
