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Organic Chemistry 2 > Exam 1 > Flashcards

Exam 1 Flashcards

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1
Q

Modern technique for structure of organic compounds: Mass Spectrometry

A

What is the size and formula of the compound?

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2
Q

Modern technique for structure of organic compounds: Infrared Spectroscopy

A

What functional groups are present in the compound?

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3
Q

Modern technique for structure of organic compounds: Ultraviolet spectroscopy

A

Is a conjugated pi electron system present in the compound?

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4
Q

Modern technique for structure of organic compounds: Nuclear magnetic resonance spectroscopy

A

What is the carbon-hydrogen framework of the compound?

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5
Q

Spectroscopy involves an interaction between

A

matter and light (electromagnetic radiation)

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6
Q

Photos

A

Waves of energy or packets (particles) of energy

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7
Q

Properties of light waves:

A

Wavelength and frequency

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8
Q

Wavelength is _____ proportional to energy

A

inversely

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9
Q

Frequency is ____ proportional to energy

A

directly

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10
Q

Electromagnetic radiation exhibits dual behavior:

A

Particle-like (photon) and wave-like

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11
Q

Wavelength (λ)

A

Distance from one wave maximum to the next

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12
Q

Frequency (v)

A

Number of waves that pass by a fixed point per unit time (measured in hertz)

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13
Q

Amplitude

A

Height of a wave measured from midpoint to peak

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14
Q

Electromagnetic spectrum

A

Range of possible frequencies of light

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15
Q

NMR region of electromagnetic spectrum

A

Radio waves

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16
Q

NMR info obtained

A

Specific arrangement of all carbon and hydrogen atoms in the compound

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17
Q

IR Region of Electromagnetic Spectrum

A

Infrared

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18
Q

IR Information Obtained

A

Functional groups present in the compound

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19
Q

UV-VIS Region of Electromagnetic Spectrum

A

Visible and ultraviolet

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20
Q

UV-VIS spectroscopy info obtained

A

Any conjugated π system present in the compound

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21
Q

On the macroscopic scale, matters appears to exhibit

A

continuous behavior rather than quantum behavior

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22
Q

Matter exhibits _____ like properties and ______ like properties

A

Particle and wave

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23
Q

Matter on the molecular scale exhibits quantum behavior

A

A molecule will only rotate or vibrate at certain rates (energies)

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24
Q

For the electrons in covalent bonds, vibrational energies are separated by

A

gaps (quantized)

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25
Q

If a photon of light strikes the molecule with the exact amount of energy needed, the light is

A

absorbed and vibrational excitation will occur

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26
Q

IR light generally causes

A

molecular vibration. Different types of bonds absorb different IR energies

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27
Q

Molecular bonds can vibrate by

A

stretching or by bending in a number of ways

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28
Q

An IR spectrophotometer irradiates a sample with

A

all frequencies of IR light

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29
Q

Frequencies absorbed by IR sample tells us the

A

types of bonds (functional groups) that are present

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30
Q

IR samples are deposited on a

A

salt plate which are transparent to IR radiation or can be dissolved in a solvent or in a KBr pellet

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31
Q

IR absorption spectrum plots the % transmittance as a

A

function of frequency. The “peaks” are called absorption bands

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32
Q

Units of frequency in IR are called

A

Wavenumbers. Values range from 400 to 4000 cm^−1

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33
Q

A signal (peak) on the IR spectrum has three important characteristics

A

Wavenumber, intensity, and shape

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34
Q

The frequency (wavenumber) for a stretching vibration depends on

A

bond strength and mass difference of the atoms bonded together.

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35
Q

The stronger the bond, the ____ stretching frequency

A

higher

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36
Q

The larger the mass difference, the ____ stretching frequency

A

higher

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37
Q

X-H wavenumber

A

4000 - 2700 cm^-1

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38
Q

C triple bonded to C wavenumber

A

2300 - 2100 cm^-1

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39
Q

C triple bonded to N wavenumber

A

2300 - 2100 cm^-1

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40
Q

C=C wavenumber

A

1850 - 1600 cm^-1

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41
Q

C=N wavenumber

A

1850 - 1600 cm^-1

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42
Q

C=O wavenumber

A

1850 - 1600 cm^-1

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43
Q

C-C wavenumber

A

1600 - 400 cm^-1

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44
Q

C-N wavenumber

A

1600 - 400 cm^-1

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45
Q

C-O wavenumber

A

1600 - 400 cm^-1

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46
Q

Region above 1500 cm^-1 in IR is called the

A

diagnostic region and the peaks in this region provide clear information

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47
Q

The region below 1500 cm^-1 is called the

A

fingerprint region. There are many signals here and it is difficult to analyze

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48
Q

The higher the s character of the carbon, the stronger the C-H bond, and so the ____ the stretching frequency of the C-H bond

A

higher

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49
Q

Alkyl C-H bonds come just ____ 3000 cm^-1

A

under

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50
Q

Alkenyl and Alkynyl C-H bonds are ____ 3000 cm^-1

A

over

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51
Q

Resonance delocalization of electrons affects the strength of a covalent bond and thus the

A

wavenumber of a stretching signal

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52
Q

The more delocalized the p electrons, the weaker the p bond, and the

A

lower the stretching frequency

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53
Q

Conjugated carbonyls have

A

lower stretching frequencies

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54
Q

When a bond undergoes a stretching vibration, its dipole moment

A

oscillated

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55
Q

Formula for dipole moment includes the

A

distance btwn the partial charges

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56
Q

Oscillating dipole moment creates an

A

electric field surrounding the bond

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57
Q

The more polar the bond, the greater the opportunity for

A

interaction btwn the waves of the electrical field and the IR radiation

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58
Q

Greater bond polarity =

A

stronger IR signals

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59
Q

If a bond is completely symmetrical, then a stretching frequency (is or is not) observed in the IR spectrum

A

is not

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60
Q

Primary and secondary amines exhibit

A

N-H stretching signals

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61
Q

secondary amines exhibit only ___ signal(s) for N-H bonds

A

1

62
Q

primary amines exhibit ____ signal(s) for the N-H bonds

A

two

63
Q

Symmetric stretching

A

Stretching in the same direction

64
Q

Asymmetric stretching

A

Stretching in opposite directions

65
Q

IR Spectrum: 1600-1850 cm^-2, check for

A

double bonds

66
Q

IR Spectrum: 2100-2300 cm^-2, check for

A

triple bonds

67
Q

IR Spectrum: 2700-4000 cm^-2, check for

A

X-H Bonds

68
Q

Mass spec can be used to identify compounds and help with

A

pharmaceutical, biotech, clinical, environmental, geological, forenscis, and many more

69
Q

Mass spec (MS) measured the

A

mass and molecular weight of a molecule

70
Q

Mass spec provides structural info by finding the

A

masses of fragments produced when molecules break apart

71
Q

Mass spec is used to determine the molar mass and ____ of a compound

A

formula

72
Q

In a mass spec, a compound is

A

vaporized, ionized, and undergoes fragmentation. the masses of ions are detected and graphed

73
Q

Most common method of ionizing molecules is by

A

Electron impact where the sample is bombarded with a beam of high energy electrons that causes an electron to be ejected from the molecule

74
Q

Mass of _____ is the same as the parent compound (mass of an electron is negligible)

A

radical cation

75
Q

If the radical cation remains intact, it is known as the

A

molecular ion (M+•) or parent ion

76
Q

Most of the radical ions in a mass spec are fragmented into a radical and a cation. The ions are deflected by a magnetic field and their _____ is detected

A

mass to charge ratio (m/z). Neutrally charged fragments are not detected

77
Q

Mass spec shows relative abundance of each

A

cation that was detected

78
Q

In mass spec, base peak is the

A

tallest peak in the spectrum and is the most abundant fragment

79
Q

In mass spec, peaks above molecular weight appear as a result of

A

naturally occurring heavier isotopes in the sample

80
Q

In mass spec, molecular weight is determined from

A

molecular ion peak

81
Q

In mass spec, if parent ion isn’t present, it’s due to

A

electron bombardment causing breakdown, “softer” methods such as chemical ionization are used

82
Q

M+1 peak results from presence of

A

13C and 1H

83
Q

Fragmentation occurs when

A

high-energy cation radical falls apart (1 fragment retains + charge and is a carbocation, and 1 fragment is a neutral radical fragment)

84
Q

1st step in analyzing a mass spec is to identify

A

M+• peak

85
Q

M/z of parent ion in mass spec equals

A

molar mass of compound

86
Q

Odd-massed M+• peaks means there is an

A

odd number of N atoms in the molecule

87
Q

An even-massed M+• peak generally indicates an

A

absence of Nitrogen, or an even number of N atoms present

88
Q

1% of all carbon atoms are

A

13C

89
Q

More carbon atoms in a compound, more abundant _____ peak is in mass spec

A

(M+1)+•

90
Q

Tertiary is (more or less) stable than primary or secondary

A

more

91
Q

Alcohols undergo two types of fragmentation

A

alpha cleavage and dehydration

92
Q

Ketones and aldehydes also undergo alpha cleavage of bond btwn

A

carbonyl group and neighboring carbon

93
Q

Amines undergo ____ fragmentation

A

alpha cleavage

94
Q

Carbonyls undergo ____ fragmentation

A

McLafferty rearrangement

95
Q

Common fragments in mass spec: M-15

A

Loss of methyl radical

96
Q

Common fragments in mass spec: M-29

A

Loss of ethyl radical

97
Q

Common fragments in mass spec: M-43

A

Loss of propyl radical

98
Q

Common fragments in mass spec: M-57

A

Loss of butyl radical

99
Q

Common fragments in mass spec: M-18

A

Loss of water (from an alcohol)

100
Q

Common fragments in mass spec: M-X (where X is an even number)

A

McLafferty rearrangement (Ketone or aldehyde)

101
Q

For degrees of unsaturation, alkanes, or unsaturated hydrocarbons, follow the formula

A

CnH2n+2

102
Q

Degree of unsaturation

A

A pi bond or a ring. For every DU in a compound in a compound, the number of Hs is reduced by 2. These are unsaturated compounds

103
Q

1 degree of unsaturation equals

A

1 unit on the hydrogen deficiency index (HDI)

104
Q

For HDI, a halogen is treated as if it were a

A

hydrogen atom

105
Q

For HDI, an oxygen (does or does not) affect HDI

A

does not

106
Q

For HDI, a nitrogen (increases or decreases) the number of expected hydrogens by one

A

increases

107
Q

Use this formula to calculate HDI

A

HDI = 1/2 (2C + 2 + N - H - X)

108
Q

If HDI = 0, molecule (does or does not) have any rings, double bonds, or triple bonds

A

does not

109
Q

General formula for Calculating DU and/or HDI

A

(Number of Carbons) - (Number of Hydrogens / 2) - (Number of Halogens / 2) + (Number of Nitrogens / 2) + 1

110
Q

Nuclear magnetic resonance (NMR) spec may be most powerful method of

A

gaining structural info about organic compounds

111
Q

NMR involves an interaction btwn

A

electromagnetic radiation (light) and the nucleus of an atom

112
Q

Magnetic moment exists perpendicular to

A

axis of nuclear spin

113
Q

Beta spin state

A

Opposing B0, higher energy spin state

114
Q

alpha spin state

A

Aligned with B0, lower energy spin state

115
Q

The more shielded a nucleus is with electron density, the

A

smaller the alpha beta energy gap

116
Q

Pulsed Fourier transform spectrometer

A

Brief pulse of radio energy (all relevant wavelengths) is used to excite the sample

117
Q

In NMR, position of peaks tells us

A

about the electronic environment of each kind of H in the compound

118
Q

In NMR, the number of signals (peaks) tells us about

A

the different kinds of hydrogens (protons) that are present in the molecule

119
Q

In NMR, the peak area (integration) tells us about the

A

number of hydrogens (protons) represented by each peak

120
Q

In NMR, signal spitting (splitting patters) tells us about the

A

information about neighboring hydrogens

121
Q

Homotopic

A

Two H’s that are in identical environments and have the same NMR signal

122
Q

Number of signals in a NMR spec indicates the

A

number of different kinds of protons in a compound

123
Q

Homotopic protons

A

If the molecule has an axis of rotational symmetry that allows one proton to be rotated onto the other without changing the molecule

124
Q

Enantiotopic protons

A

If the molecule has a plane of reflection that makes one proton the mirror image of the other

125
Q

Diastereotopic

A

Compounds that are not chemically equivalent

126
Q

2 protons on a CH2 group will be equivalent if there are

A

no chiral centers in the molecule

127
Q

2 protons on a CH2 group will not be equivalent if there is

A

a chiral center in the molecule

128
Q

Downfield has (high or low) field strength

A

low

129
Q

Upfield has (high or low) field stregth

A

high

130
Q

Shielded protons require a ____ external magnetic field to be excited at the same energy as deshielded protons

A

stronger. They have smaller energy gaps and absorb lower energy wadio raves

131
Q

Deshielded protons are in the ____ area

A

downfield

132
Q

Shielded protons are in the ____ area

A

upfield

133
Q

Diamagnetic anisotropy

A

Different regions of localized space have different magnetic strengths

134
Q

Integration (area) under peak quantifies the

A

relative number of protons giving rise to a signal

135
Q

J value (coupling constant)

A

Distance between peaks of a splitting pattern measured in units of Hz

136
Q

Carbon - 13

A

Only carbon isotope with a nuclear spin. Natural abundance is 1.1%

137
Q

In 13C NMR spec, each type of Carbon produces

A

one signal or peak. There is no C-C coupling that causes signal splitting

138
Q

Proton decoupled spectrum

A

Signals for each carbon are singlets (no 13C-H splitting is shown)

139
Q

Proton coupled spectrum

A

Each different carbon is splitted by H bonded to it; n+1 rule for 13C-H splitting where n=# of H bonded to carbon in question. Signal for each C has n+1 peak

140
Q

Chemical shift for 13C NMR

A

Chemical shifts occur btwn 0 and 220 ppm

141
Q

In 13C NMR, sp3 signal is at

A

0 to 9 wavelength

142
Q

In 14 C NMR, sp2 C is at

A

110 to 220 wavelength

143
Q

In 13C NMR, C(=O) is at

A

low field, 160 to 220 wavelength

144
Q

In 13 C NMR, summary (does/does not) affect number of signals

A

does

145
Q

MRI (magnetic resonance imaging) instruments are essentially

A

1H NMR specs

146
Q

Vibrating bonds can be demoted to a lower vibration state by

A

emitting IR radiation. Ex; night vision goggle or mammograms

147
Q

Blood can be analyzed with

A

Mass spec bc it can be used to detect abnormal blood levels of amino acids, fatty acids, and sugars

148
Q

Drug purity can be determined with

A

mass spectrometry. can measure blood or urine levels for it

149
Q

Bacterial infection and specific protein biomarkers for cancer can be detected with

A

mass spec.

150
Q

Microwaves are a direct application of quantum mechanics and spectroscopy dues to the fact that it

A

causes rotational excitement

151
Q

Impurities of Heparin Sodium can be detected with

A

NMR

Organic Chemistry 2 (1 decks)

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