General Information

Question 1

what is the formula for degrees of unsaturation?

Answer 1

(2C + 2 + N - X - H)/2

Question 2

in the degrees of unsaturation formula, what does each variable represent?

Answer 2

C = carbon, N = nitrogen, X = halogens, H = hydrogens

Question 3

if the DOU is one, what does that indicate?

Answer 3

there is only 1 carbon ring or a pi bond

Question 4

if the DOU is 2, what does that indicate?

Answer 4

there are 2 carbon rings or 1 carbon ring plus a pi bond

Question 5

if the DOU is 4, what does that indicate?

Answer 5

there is a high likelihood of an aromatic ring

Question 6

what types of vibrational modes are IR active?

Answer 6

asymmetric stretching and bending

Question 7

what is the unit for IR vibrating frequency?

Answer 7

wavenumbers

Question 8

is the wavenumber increases, what happens to wavelength and energy?

Answer 8

wavelength decreases and energy increases

Question 9

compared to IR bending, does stretching require more or less energy, and does this lead to an increased or decreased wavenumber?

Answer 9

it requires more energy, resulting in a higher wavenumber

Question 10

do stronger bonds have a higher or lower wavenumber?

Answer 10

they have a higher wavenumber

Question 11

what does proton NMR reveal?

Answer 11

the relative numbers of hydrogens in different chemical environments within a molecule

Question 12

what type of information is provided by NMR?

Answer 12

the number of signals, integration, chemical shift, and multiplicity

Question 13

what does each NMR signal represent?

Answer 13

a group of chemically equivalent protons

Question 14

when are two hydrogens chemically equivalent?

Answer 14

if they can be interchanged by a plane of symmetry or by bond rotation

Question 15

in NMR, what is integration?

Answer 15

it is the area under the signal and is proportional to the number of hydrogens

Question 16

what information does the chemical shift give us?

Answer 16

it provides us with information about how rich or poor a hydrogens chemical environment is

Question 17

what is the inductive effect on ppm?

Answer 17

more electronegative atoms nearby results in a higher ppm

Question 18

what is multiplicity and what does it reveal?

Answer 18

the splitting of a signal into multiple different lines and reveals connectivity

Question 19

how does vicinal coupling (3-bond coupling) affect multiplicity?

Answer 19

it often leads to splitting because the hydrogens tend to be chemically different

Question 20

what is the N + 1 rule?

Answer 20

the number of lines in a signal is n +1, with n being the number of chemically non-equivalent neighbors