Chem 2 Lab Midterm

What is IR?

An analytical tool used to identify organic functional groups

In a transmittance graph, what does a small peak represent?

Little absorption

In a transmittance graph, what does a big peak represent?

Big absorption

What do functional groups do?

Gives molecule function

IR is what type of technique?

Non-destructive vibrational: it makes molecules vibrate

What does IR stand for?

Infrared spetroscopy

High frequency = _______=_________

High energy, short wavelength

Wavelength is converted into what?

Wave numbers

What can be determined from the placement of peaks in IR?

Bond strength

More bonds means what?

More strength

What happens when two waves have the same frequencies?

They add to eachother

What happens when two waves have different frequencies?

They destroy each other

All bonds do what?

Vibrate

Everything is going in a what?

Wavelike motion

When an organic compound is irradiated with a specific IR frequency that matches a natural vibrational frequency, what happens?

Resonance (absorption) takes place

What does resonance lead to?

Different modes of vibration, like stretching, bending, and translating

What does this image represent?

stretching of a bond

What does this image represent?

bending of a bond

What is the functional group of R-NH2?

Amine

What is the peak of R-NH2?

3400 cm^-1

What is the functional group of R-OH?

Alcohol

What is the peak of R-OH?

3300 cm^-1

What is the peak of aromatics?

3050 cm^-1

What is the carbon peak of aromatics?

1600, 1500 cm^-1

What is the peak of aliphatic?

2950 cm^-1

What is the bends of aliphatic?

1450-1350 cm^-1

What is the peak of carbonyl?

around 1700 cm^-1

What is the peak of fingerprint?

below 1250 cm^-1

aromatics and aliphatics never touch which number?

3000

What are colligative properties?

those that depend on the amount of solute (concentration) and not on its identity

what are colligative properties of a solution?

• Lowering of vapor pressure

• freezing point depression

• boiling point elevation

• increase in osmotic pressure

what happens to the vapor pressure if a non volatile solute is added to a solvent?

it lowers

what is the van hoff factor?

the amount of solute dissolved in particles

what is the formula for freezing point depression?

Delta TF=iKfm

What is the formula for molality?

moles of solute/kg solvent

what is the formula for molecular weight?

mass/moles

What is TLC?

Analysis of organic components in a mixture

TLC is a separation and purification based on what?

polarity

TLC is made of what?

plastic or aluminum with a thin layer of silica on top

Is silica polar?

yes

What does TLC stand for?

Thn Layer Chromatography

Graphite is a..

network covalent solids

Does graphite dissolve?

No, doesnt dissolve in anything

How do you determine the identity of an unknown?

Compare it to a standard

What is the substance if you do not have a standard?

The substance is unknown

What does it mean when a substance moves slower on the silica?

the substance does like the silica and is very polar

What does it mean when a substance moves fast on the silica?

the substance doesn’t like the silica and is the least polar

what is the solvent front?

marks the maximum distance the liquid solvent has migrated from the original baseline

what is the stationary phase in TLC?

the silica dioxide

How does the liquid move up the TLC?

By capillary action

What is the mobile phase in TLC?

The solvent moving up the TLC

What is RF and its formula?

Retetntion factor; RFsubstance=Distance of substance from baseline/total length between baseline and solvent front (x)

What does RP HPLC stand for?

Reverse Phase High Performance Liquid Chromatography or High Pressure Liquid Chromatography

What does reverse phase mean?

Non polar stationary phase

RP HPLC is the best what?

separation and purification technique

Separation is based on what?

polarity

How do you determine the concentration of an unknown?

Compare it to the standard concentration, building a calibration curve/standard curve and by applying Beer’s Law

What is Beer’s Law’s formula?

A=abc

where:

A=absorbance

a=constant

b=path length

c=concentration

What do you get from a HPLC?

a chromatogram

What is retention time?

The time at which the chemical comes out

When you have a chromatogram, what comes out first?

Polar things

When you have a chromatogram, what comes out last?

Non-polar things

What does the size of a peak on a HPLC mean?

Concentration

The bigger the peak, the what the concentration?

The higher the concentration

What is Beer’s Law in words?

the linear relationship between absorbance and concentration

the line of Beer’s Law has to go through what in a graph?

The origin

What does A represent in terms of polarity?

The most polar substance

What does C represent in terms of polarity?

the most non-polar substance

What does B represent in terms of concentration?

Highest concentration