Download Investigate molecules with light

Investigate molecules with light
ICCE – ECRICE 2012, July 15-20, R2012, Rome
The molecule, from moles, which means "mole", "small amount",
is a collection of at least two atoms (the same element or several
elements) are joined by a covalent chemical bond, i.e. when they
are bound together by sharing one or more pairs of electrons.
The molecules are the fundamental constituents of most of the
organic matter present in the universe, as well as the oceans and
the atmosphere.
THEIR SHAPE
The shape of molecules, i.e. how they are distributed in the
different components, is a feature that affects not only the
physical properties and chemical ones. This is even more
apparent when we consider the organic molecules and their
activities. Many molecules, although composed from the same
atom and combination, described with the same formula, acquire
different characteristics when atoms are distributed in space in
different ways. It says that two or more molecules have the same
formula when they have the same number and type of atoms
that make up. In particular, two atoms are "of the same type" if
they belong to the same chemical element (i.e. If they have the
same atomic number).
THEIR POLARITY
Any molecule that contains two different generic but atoms
bound together chemically, enjoys the polar property. This
peculiarity, depending on their different ability to attract
electrons, is because of the different location between the
Centre of gravity of positive charges (protons) and negative
(electrons) that generates an electric dipole (system consisting of
two equal and opposite electric charges to sign and separated by
a constant distance over time).
This property originates from:
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the polarity of the covalent bonds that form the
molecule, which in turn depends on the difference in
electronegativity of the atoms involved in the bond. The
larger the difference in electronegativity, the greater the
polarity
the symmetry in molecule form that depends on the
mutual arrangement of its individual components
The polarity of the molecule influence, in turn, other properties:
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chemical reactivity with other molecules
bond strength and cohesion
solidification temperature and boiling point
miscibility and solubility in the presence of solutions
electrical conductivity, as well as substances that
solutions
THE ISOMER
It's that phenomenon for which substances which, while having
the same formula (share molecular weight percentage
composition of atoms) have different physical properties and
very often even different chemical behavior. Therefore, the
compounds that have the characteristics described above are
called isomers and are as below, labeled:
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Constitutional isomers (or structural): they have
identical formula brute but different connectivity, which
are compounds with the same molecular formula but
different structural formula. They, therefore, different
physical and chemical properties, due to the difference
of the bonds between the elements that make up the
molecule. In turn are divided into:
 Constitutional isomers of chain: their distinctive
factor is the structure of the "skeleton", the
carbonaceous presence and position of branches
or rings; they have different physical properties,
Chemical reactivity but pretty similar
 Constitutional isomers of position: the element
that characterizes them is the location of
multiple ties or groups containing atoms other
than carbon and hydrogen; they, belonging to
the same class of compounds, despite different
physical properties, their chemical reactivity
similar
 Constitutional isomers of functional group:
despite having the same formula, have different
functional groups and, consequently, their
chemical and physical properties very different
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Stereoisomers: they have the same formula, same
connectivity, but they are not stackable owing to
different three-dimensional orientation of atoms in
space. They are distinguished:
 Diastereo-Isomers: there are two isomers in
which one is not the mirror image of the other.
Among diastereo-isomers:
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Geometric isomers (cis-trans): only present in molecules
in which two carbon atoms linked by a double bond are
both linked in turn to two different groups; more
generally, they occur in molecules whose structure
prevents free rotation around one or more links. The
physical properties of these isomers are different, while
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their chemical reactivity is generally similar. It's worth
remembering that there are notable exceptions due to
the particular geometrical configurations
Isomers conformers (or conformational): while no one
stereo center (carbon atom become tethered to four
Chiral because atoms or four different groups of atoms)
are stereoisomers that are achieved when the atoms
revolve around single bonds, giving rise to different
conformations of the molecule. They have the same
formula, same connectivity but are not stackable
Rotameri isomers: are conformers that differ by the
twisting of one (and only one) link. It is important to bear
in mind that the vision must be "front", i.e. observed
frontally the axis of the
 Isomers enantiomers: they are molecules that exhibit
stereo genic element i.e. atoms because of whom admit
two isomers molecules that have a mirrored form of the
other non-stackable
ISOM
COSTITUZIONAL
of FUNCTIONAL
GROUP
of CHAIN
of POSITION
ERS
STEREOISOMERS
DIASTEREO-ISOMERS
GEOMETRIC ISOMERS
ENANTIOMERS
CONFORMERS
ROTAMERI
THE CHIRALITY
It is the property of any hard object (or a spatial arrangement of
points and atoms) to have a mirror image in three dimensions is
not stackable. An object with this property is called chiral.
THE ENANTIOMORPHISM
It is the geometric transform that converts an object into its
mirror image. As a result, you say enantiomorphic a pair of
molecular entities that are mirror images of each other and not
overlap; in the case of molecules, enantiomers instead of
enantiomorphic.
THE OPTICAL ACTIVITY AND THE OPTICAL ROTATION
It is the property of rotate the plane of polarized light vibration
possessed by Chiral chemicals and then optically active. The
optical power is the measure of optical activity.
With the general term wave is a disturbance that comes from a
source and propagates in time and space, delivering energy
without result associated with movement of the subject. Waves
can propagate through a material or, more simply, in a vacuum.
THEIR CHARACTERISTICS
A wave can be characterized by a single oscillation or a sequence
(or train) with wave-like features. In general, the waves are
formed by:
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crest
belly
wave fronts of propagation: present only in trains of
waves and can be categorized into transverse or
longitudinal
THE REFERENCE PARAMETERS
The waves differ from one another in order to:
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amplitude
wavelength
period
frequency
phase
speed of propagation
energy and power associated with the speed of
propagation
THE MEANS OF PROPAGATION
The medium in which the waves travel can be classified into:
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limited or unlimited
homogeneous
isotropic or anisotropic
THE EFFECTS
Each wave takes a common behaviour in standard situations and
may undergo the following phenomena:
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amplitude attenuation during propagation of the
medium
meditation
refraction
diffraction
dispersion
interference
Doppler effect
WAVELENGTH TYPES
Based on different characteristics of waves, they can be classified
into categories concerning:
the type of medium:
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mechanical waves (sound waves)
non-mechanical waves (light waves)
the size of the medium in which they propagate:
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linear or one-dimensional waves (swing by a rope)
two-dimensional waves (circular waves on a water
surface)
three-dimensional waves (sound waves)
their direction of propagation vector:
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longitudinal waves (pressure waves)
transverse waves (electromagnetic waves) propagation:
plane waves (waves on the water surface)
spherical waves (pressure waves)
cylindrical waves (adjacent waves an antenna)
the medium in which it propagates and physical characteristic
that it represents:
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elastic waves or displacement
electromagnetic radiation (light, radio waves, ultraviolet
rays, x-ray)
THE SINUSOIDAL WAVES
They are a particular solution of the general equation of waves:
v=
V = wave frequency
T = wave periodicity
𝟏
𝑻
In fact, if we consider a one-dimensional wave, in describing it,
you consider the horizontal position x of the impulse and time T
that we observe the wave itself: the amplitude of the oscillation y
of the particles around the equilibrium position is in terms of
these elements:
y= f(x,T)
y = swing
x = the time dimension
T = time
The viewpoints are two:
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choosing to evaluate the temporal dimension (x fixed),
we will state the y swinging time dependence t:
y= f(T)
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choosing instead to focus on a medium perturbed at a
certain moment (T set) ot-hold sway y expressed as a
function of position x:
y= f(x)
THE ELECTROMAGNETIC WAVES
An electromagnetic wave is a disturbance of electric and
magnetic nature simultaneously that propagates through space
and that can carry energy from one point to another. This
disruption is the simultaneous vibration of two intangible entities
called the electric field and magnetic field around their
equilibrium position (which corresponds to no disruption). An
electromagnetic wave travels in the direction perpendicular to
the direction of oscillation of the fields, it is, therefore, of a
transverse wave. Electromagnetic waves propagation
characteristics in the media or in presence of obstacles depends
on the frequency (and therefore wavelength).
WHAT HAPPENS IN AN ELECTROMAGNETIC WAVE
An electron building generates, because of his position, an
electric force in the surrounding space, the electric field, which
decreases as the inverse square of the distance. By swinging a
first electron, the electric field is perturbed at the points around
due to the change from the electron during its swing. A variation
of the electric field get black-a magnetic field. These swings of
the electric field — and therefore also of the magnetic field —
propagate by electron generating electromagnetic waves. A
second electron is stationary at a certain distance from the first,
begins to wobble soon invested by electromagnetic wave
produced by the electron. Even the electric field of the second
electron, then, will be disrupted by its oscillations and throws
itself a magnetic field, allowing the wave propagation. The sizes
of the wave, i.e. its breadth, give a measure of the intensity of
the electric wave.
The radiation of an electromagnetic wave is composed of
electromagnetic waves, which consist in swing concert-nanny of
an electric field and a magnetic field. These on-de propagate in
the direction orthogonal to that of oscillation.
Finally, an electromagnetic wave is emitted whenever a charged
particle undergoes acceleration due to some force.
THEIR CLASSIFICATION
It is customary to classify the different magnetic waves:
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radiofrequency waves
microwave
infrared spectrum
visible spectrum
light, produced by quantum transitions of atoms or
molecules. Depending on the wavelength, it affects the
retina
ultraviolet rays (Sun)
x-rays
gamma rays
THE LINEARLY POLARIZED LIGHT
Linearly polarized light (or polarized on a plane) is the energy
that results from ordinary light passing through an optical
polarizer filter, where the emerging light is a beam whose electric
vector vibrates on a single floor. Actually, the plane-polarized
light is the resultant of two circularly polarized components
direct opposite, rightward and leftward, in concordance with the
same phase and frequency and amplitude. When polarized light
interacts with a chiral medium, his plan of polarization varies its
orientation relative to the direction of propagation: such
distortion is known as optical rotation, whereby the optical
activity is the ability of a substance, called optically active, to
rotate the plane of polarized light.
GLOSSARY
Belly: lowest point wave
Crest: highest point of a wave
Cylindrical wave: wave that unfolds spatially so symmetric with
respect to an axis
Dispersion: Wave Division under waves in dependence of their
frequency
Doppler effect: frequency shift of a periodic wave traveling
relative to the direction of observation both swinging and varying
their towards a special flavor and intensity
Elastic wave: wave mechanics in which the physical properties of
the medium are elastic and that has verified the Hooke's law
Electromagnetic radiation: form of energy associated with the
electromagnetic interaction and the propagation in the space
time of the electromagnetic field in the form of electromagnetic
waves
Gamma ray: wave with a wavelength range of 1 * 10-10 m and 1
* 10-14 m. Originates from nuclear power and is used in special
therapies
Gravitational wave: fluctuation of gravitational field
Homogeneous medium: physical properties in an anywhere do
not vary as a result of translation
Infrared spectrum: wave of wavelength ranging from 1 mm to
7.8 * 10-7 m. This is a wave produced by excited molecules and
hot bodies; it is used in industry and medicine
Interference: vector sum (even nothing) of two waves that come
into contact with each other
Isotropic medium: physical properties in an anywhere do not
change as a result of rotation from that point
Limited medium: medium that has a finite extension
Longitudinal wave: the vibration agrees with the direction of
wave propagation
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magnetic field
Mechanical wave: wave that propagates only in non-material
means empty because they exploit the properties of elasticity of
the medium for their propagation
Microwave: wave with a wavelength of between 0, 3 m and 1
mm. This category, produced by special electronic products, used
in radar systems and those of special media
Non-mechanical wave: wave that propagates in non-material
means that the vacuum
Ocean wave disturbance: surface propagating into the water
Optical rotation: rotation, in degrees, of the plane of polarized
light caused by the passage of this through a solution of an
optically active substance
Optically active substance: substance able to rotate the plane of
polarized light vibration
Ordinary light: light consists of electromagnetic waves that
vibrate in all directions perpendicular to the direction in which it
travels, i.e., spreads in the form of waves develop on different
planes along the line of propagation. Its range consists of two
components that vibrate on planes perpendicular to each other
Plane wave: steady frequency wave whose wave fronts are
infinite parallel planes of constant amplitude normal to the wave
vector
Radio frequency wave: waves with wavelengths ranging from a
few miles up to 0.3 m. This category is used in the transmitting
system of radio and television and is generated by special
electronic devices
Reflection: change of direction of wave propagation due to a
clash with a reflective material
Refraction: wave direction change caused by the change of the
means of propagation (example: different densities)
Sound: mechanical wave that propagates through gas (typically
air), liquid or solid, whose frequency can be perceived by the
auditory apparatus
Spherical wave: the wave front is a sphere and, therefore, its
source is a point so that the wave front to propagate in
proportion to the distance r from the source
Translation: affine transformation of Euclidean space which
moves all points a fixed distance in the same direction
Transverse wave: the vibration is perpendicular to the direction
of wave propagation
Ultraviolet ray: wave whose wavelength values are between 107 m 3.8 * and 6 * 10-7 m. It is used in some medical applications
and application in sterilization processes
Visible spectrum: narrow band of audible waves from the retina
of the human eye. This is a wave with a wavelength of between
7.8 * 10-7 m and 3.8 * 10-7 m
Wave propagation: diffraction (example: when passing through
a narrow slit)
Wave fronts of propagation: sets of points agreed that vibrate,
so that, for each of them, the displacement from the equilibrium
position to assume the same value in every moment
Wavelength: distance between two crests or between two
wombs of his wave form
Width: maximum variation of greatness in a periodic oscillation
X ray: wave extending from 1nm to 1 * 10-11 m. Produced by
electron quantum transitions innermost atomic structures (more
strongly bound to the nucleus), is very penetrating
The polarimeter is the instrument used to measure the optical
rotation of optically active substances.
DESCRIPTION
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light source: LEDs of different colors with wavelengths (λ) different
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Switch to the choice of led
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Lens
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First polarizer
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Tube with sample
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Second polarizer for optical rotation measuring
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Goniometer and nonius
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Rotating disk manual
9.
External protective cylinder complete with base
TECHNICAL CHARACTERISTICS
Angle measurement accuracy: ± 0.1 mm
Tube sample length: 100 cm
Weight: 3.25 Kg
Dimensions: l 22 cm; h 122 cm; p 22 cm
Monochromatic light source: led
OPERATING METHOD
PREPARATION:
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Measuring of white to attach the position of zero
Fill the tube with the solvent to analyze
Place the sample in the polarimeter tube
Place the goniometer on head to the tube
Switch on the led of the desired color by selecting it with
the switch
Rotate the goniometer until the led goes dark
Check the position of zero
MEASURING THE OPTICAL ACTIVITY:
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Prepare the solution to be analyzed
Pour the solution inside the measuring tube
Insert the sample tube with solution in the polarimeter
Place the goniometer on head to the tube
Measure the level of the liquid in the tube
Switch on the led of the desired color by selecting it with
the switch
Rotate the goniometer until the led goes dark
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Read the value on the goniometer and calculating the
angle difference with sample zero
Repeat the measurement halving the length of the path
(or halve the amount of fluid) into the measuring tube
If the new angle corresponds to α/2 or α/2 ± 180°, the
substance is called dextrorotatory, instead if you get
values equal to α-180°/2 or α-180°/2 ± 180° the
substance is called levorotatory
Apply the formula of optical rotation to get the
concentration of the compound or the specific optical
rotation of substance
𝛂=𝐜∙𝐥∙𝐤
α= angle of experiment rotation experiment
c= concentration of the compound
l= length of path
k= specific optical rotation
WARNINGS
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The instrument must be kept clean and breezy with
temperature and humidity within the normal range
(about 20° C 50% UHR)
After using the measuring pipe must be carefully cleaned
with distilled water
Do not use abrasive materials to clean the optics of the
instrument (including paper)
Hold the instrument always covered (when not in use) to
prevent the introduction of dust
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Do not disassemble the instrument; mistakes in
assembling mechanical alignment that can irreparably
undermine the accuracy are instrument