Ochem 2 Test 1

What does mass spectrometry allow us to determine

molecular mass and molecular formula

What does Infared (IR) spectroscopy allow us to identify?

functional groups

What does Nuclear magnetic resonance (NMR) spectroscopy provide us with

NMR provides information about the carbon-carbon and carbon-hydrogen framework

What does all spectroscopy involve the relationship between

it involves the relationship between matter and light (electromagnetic radiation)

With electromagnetic radition, as energy increases, frequency what?

increases

What is this symbol for?

wavelength. distance from any point on one wave to the corresponding point on the next wave

What does v stand for?

The number of waves that pass a given point inone second. Frequency.

What will we use to determine frequency (v)?

wavenumber ṽ (cm^-1)

What are bonds similar to? What are the two types?

bonds are like vibrating strings.

The two types are stretches and bends.

The two types are stretches and bends

What type of vibration of a bond is a vibration along the line of the bond that changes the bond length

stretch

What bond vibration is a vibration that does not occur along the line of the bond? Changes the bond angle and occurs in molecuels of three or more atoms

a bend

What do bonds absorb that leadss to vibration?

electromagnatic radiation

What is true of the frequency of radiation each bond will absorb

A given bond will always absorb the same frequency of radiaiton

What does the IR spectrum really tell us?

Of the light that we sent through, how much was transmitted?

A weaker bond will have…

lower energy and lower wavenumber

a stronger bond will have….

higher energy and higher wavenumber

What are the three big characteristics that help us to determine what bond is present in a IR graph?

wavenumber, intensity, and shape.

What is true of bond type and frequency?

triple bonds have the highest frequency, while single bonds have the lowest frequency.

The lighter the atom the….. the wave number

higher

Single bonds typically stay on the lower end of the IR spectrum. This is true except for….

Bonds to H.

What are the two halves of the IR spec?

the diagnostic region and the fingerprint zone. We will mostly stay in the diagnostic region.

The higher the ________ of the carbon, the stronger the C-H bond and the higher the stretching frequency of the C-H bond

s character (sp3,sp2,sp)

remember that s character is determined by how many attachment points you have -1 not by the number of lines coming off of the central carbon.

If you have a single bond you have an

alkane

if you have a double bond you have an

alkene

if you have a triple bond, you have an…

alkyne.

If you know you potentially have an alkane, alkene, or alkyne, where should you draw the line in order to further look into things? Where might you expect to see each of the items?

You should draw a line at 3000.

You can expect to see your Alkane right at 3000, your Alkene a little after 3000, and you Alkyne far away from 3000 going up.

if a Double bonded C=O bond has significant single bond character due to resonance it will have ______ frequency

lower

What two factors is intensity of an absorption band dependant on?

-The polarity of the bond (more polar more intense)

-the number of the bonds (more bonds, more intense)

What type of nuclei can be detected with NMR?

Nuclei with odd number of protons and or odd number of neutrons have a property called spin that allows them to be detected

What spin state are the nuclei that align with the applied magnetic field in

They are in the alpha spin state. This is the lower energy spin state

What spin state are the atoms that align themselves against the applied magnetic field in?

Beta spin state. This is the higher energy spin state

What is shot at the nuclei to change their spin state?

radio waves

_____ decreases the degree to which a nucleus experiences the applied magnetic field

electron shielding

What does Bo stand for

Applied magnetic field

Protons in electron-rich environemnts are ____ sheilded and appear at ___ frequencies on the ____ side

more, lower, right side of the spectrum

Protons in electron-poor environemnts are ___ sheilfed appear at a _____ frequency and appear on the ____ side of the spectrum

less, higher, left side of the spectrum

What are the four primary points of interest in NMR

-Number of signals

-chemical shift (x axis)

-integration (little number on chart)

-splitting/multiplicity

Protons in the same environment are called _________ and they will produce only one signal.

chemically equivilent

The position on the x axis at which a signal occurs in an NMR spectrum is called the ______. It tells us the nature of the chemical environemnt,etc

chemical shift

the closer the electronegative atom, the more it deshields the protona and the signal is pushed ____

downfield

The less close to the electronegative atom the more ________ it will be

upfield

the more _____ a structure has, the more electronegative and thus downfield it will be

carbon,

this is because carbon is more electronegative than hydrogen

When you have C=C or triple bond, the hudrogen attached will shift______-

downfield

what is the chemical shift for an Aryl? (Hydrogen attached to an aromatic structure)

6.5-8

What is the chemical shift of an aldehyde

around 9.7

what is the chemical shift of a carboxylic acid?

10-13

the number of signals corresponds to….

the number of unique hydrogens/ number of hydrogen environments

the chemical shift corresponds to…

sheilding/desheilding. tells us the environemnt of the hydrogens

What does integration indicate?

the relative number of protons giving rise to a signal

what should you do if you cannot round during integration?

divide by the smallest number, if you still cant do it, multiply by 2

What is the rule that is used to determine the number of splits in a splitting pattern, coupling pattern, or multiplicity?>

N+1.

Go to the next carbon and see how many hydrogens ot has that plus 1 is your numnber.

What is it called when we have one peak?

singlet

what is it called when we have two peaks?

doublet

what is it called when we have three peaks?

triplet

What is it called when we have four peaks?

quartet

What is it called wehn we have five peaks?

quintet

what is it called when we have six peaks

sextet

what is it called when we have seven peaks

septet

what is it called when there is no symmetry and we have mutliple groups?

multiplet