Organic Chemistry: Lab Techniques, Separations and Spectroscopy Part II Flashcards Preview

Organic Chemistry > Organic Chemistry: Lab Techniques, Separations and Spectroscopy Part II > Flashcards

Flashcards in Organic Chemistry: Lab Techniques, Separations and Spectroscopy Part II Deck (31):
1

What is the general principle of spectroscopy?

The general principle of spectroscopy is that molecules absorb energy in order to raise to specific excited states. This energy state can be achieved by absorbed photons, ect.
The difference you see once these atoms reach their ground state can reveal the identity of the atoms you are looking for.

2

What is the general principle of mass spectrometry?

Mass spectrometry ionizes compounds, and then exposes them a magnetic plates. The degree by which the molecule is shifted towards the plate reveals the relative mass of the compound,

3

What is the general principle of UV/ Visible light spectroscopy?

The general principle is that when an atom is energized and then goes back down to it's normal state again, it can release a specific color.

However, remember that the color that is absorbed IS NOT the same color that is released, but rather it's pair in the color spectrum

4

What are the complementary color pairs?

The complementary color pairs are
1) Violet-yellow
2) red-green
3) orange-blue

5

What is the principle of IR spectroscopy

IR spectroscopy is the principle that from wavelengths from 2.5-20 wavelength cause bonds in organic molecules to vibrate

6

What do the vibrations in the bonds help us to determine?

The vibrations correspond to certain frequencies, which then are linearly related to wave numbers. Wave numbers are expressed at cm-1

7

What are the x and y axis in the Infrared Spectroscopy graph?

X axis is the wave number, while the Y axis is the transmittance.

8

Why are the peaks in IR peaks "upside down"?

They are upside down as transmittance means the radiance that an atom has/ radiation it gives out. Obviously, the less transmittance, the more energy that is absorbed and not radiated, so the peaks are faced downwards.

9

What is the frequency/wavenumber range for C=O bonds? What is the nature of this peak?

1735-1680
Strong peak

10

What is the frequency/wavenumber range for C=C bonds? What is the nature of this peak?

1680-1620
variable peaks

11

What is the frequency/wavenumber range for alkyne bonds? What is the nature of this peak?

2260-2100
variable

12

What is the frequency/wavenumber range for " C triple bond N "? What is the nature of this peak?

2260-2220
variable

13

What is the frequency/wavenumber range for C-H? What is the nature of this peak?

3300-2700
variable

14

What is the frequency/ wavenumber range for N-H? What is the nature of this peak?

3100-2500
moderate

15

What is the frequency/ wavenumber range for O-H? What is the nature of this peak?

3650-3200
broad

16

What is a good way to remember IR frequencies?

Split the bonds into "pairs"


C=O :1735-1680
C=C:1680-1620
both are complementary and have a range approx 60

C triple bond C :2260-2100
C triple bond N:2260-2220
both triple bonds start of with same wavenumber

C-H:3300-2700
N-H:3150-2500
O-H: 3650-3200

17

What are the basics you should know for NMR spectroscopy?

For NMR spectroscopy, the basic tenets are
1) Unique hydrogens
2) Splitting
2) Deshielding

18

How do you determine if hydrogens are unique or not?

You can tell that they are unique by seeing how the carbon they are bonded to bonds with other atoms. Similar bonding equates to similar hydrogens. Different bonding equates to unique hydrogens

19

How do you calculate splitting?

You calculate splitting by counting the number of different hydrogens that are connected to the carbon that has the hydrogens you are counting for.
Then add 1

20

Describe the X and Y axis of the NMR graph.

The X axis is intensity,
whitle the Y axis is ppm. The Y axis's numbers decrease from left to right, just like the IR spectroscopy.

21

State the relationship between deshielding and location of peaks on the graph

The more deshielded a H atom is, the more to the left it will be
"to the left, to the left"

22

What is the relationship between s ratio in bonding and the position of the H peaks on the graph?

The more S character a bond has, the more deshileded an atom is, as there is less electron density in the hydrogen, thereby shifting the peak to the left.

23

What is the Y axis/ppm number for phenols, and alkenes, respectively?

6.5-8ppm
6ppm

24

What is the ppm for carboxylic acid hydrogen attached to the O?

10-13ppm

25

What is the ppm for alcohol compounds in general?

2-5 ppm

26

What is the ppm for Alkynes?

2 ppm

27

What is ppm for benzylics and alkyls attached to halogens, NH2 , or OR?

2.5-3.5 ppm

28

What is ppm for aldehydes?

9-10 ppm

29

What is ppm for alkyls?

0.1-2 ppm

30

What is ppm for vinyls?

5-6 ppm

31

What is an overall picture of what the pm values and the hydrogens they generally describe?

1) Alkyl Hydrogens: around 0-2 ppm


2) Alcohol: 2-5 ppm
3) Alkyne: 2ppm
4) Alkyls atached to NH2, OH, or halogen: 2.5-3.5
5) Benzylics: 2.5-3.5

6) Vinyl:5- 6 ppm
7) Alkene (opposite group config. to vinyl) : 6ppm

6) H attached to cyclohexene: 6.5-8 ppm

7) Aldehyde: 9-10 ppm
8) Carboxylic acids: 10-13 ppm