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What is absorption spectroscopy? Absorption spectroscopy is the measurement of the amount of light ab
sorbed by a compound.
What is the process of infrared spectrometry? Infrared spectrometry measures the vibrations of bonds an
d provides evidence of functional groups present.
What is mass spectrometry? Mass spectrometry breaks molecules using electrons to determine the mole
cular weight and formula of a compound.
What is the process of electron impact ionization in mass spectrometry? Electron impact ionization is a pr
ocess in mass spectrometry where an ion source bombards a molecule with electrons, knocking out additi
onal electrons and creating a radical cation corresponding to the mass of the original molecule.
What is a molecular ion in mass spectrometry? A molecular ion is a radical cation corresponding to the m
ass of the original molecule in mass spectrometry.
What is the purpose of sorting ions by mass in mass spectrometry? Sorting ions by mass in mass spectr
ometry creates a graph where the x-axis represents masses and the y-axis represents the number of ions
of each mass.
What is the significance of peaks in mass spectrometry? Peaks in mass spectrometry represent the pres
ence of certain functional groups or fragments in a compound.
Mass Spectrum of Hexane "<img src=""paste-5c42b70d8fb63f98a7c327ed7c0a664d8a8c492c.jpg"">"
Frgmentation with ethyl cation gives rise to what ethyl frgment? m/z 29
Fragmentation ethyl cation and butyl radical "<img src=""paste-dad993bd479e388d9a08775365a1f02d13
bd4ef3.jpg"">"
What does a symmetric celavage of hexane lead to? Propyl Cation and Propyl Radical
Cleavage is to pentyl cation m/z 71 and methyl radical is... weak because the methyl radical is less stable
than a substituted radica
"Cleavage to give a methyl cation <span style=""color: inherit;""></span><img alt=""inline style open pare
ntheses m divided by z thin space 15 close parentheses"" src=""paste-2797f55181e77865c392e43e46ca
57156acd71cc.png"">&nbsp;and a pentyl radical is not visible because&nbsp;" the methyl cation is less st
able than a substituted cation. The stability of the cation is apparently more important than the stability of t
he radical, since a weak peak appears corresponding to loss of a methyl radical, but we see no cleavage t
o give a methyl cation.
FFragmentation in the mass spectrometer gives ____ cations whenever possible resonance-stabilized
<div><div>The most common fragmentation of alkenes is cleavage of an ___ bond to give a resonance-st
abilized __ cation.</div></div> <div><div></div></div> allylic&nbsp;
Compounds containing aromatic rings tend to fragment at the carbon (called a <em>benzylic</em> carbo
n) ___ to the aromatic ring. Such a cleavage forms a resonance-stabilized ___cation. next, benzylic&nbsp
;
Ethers, amines, and carbonyl compounds can also fragment to give resonance-stabilized cations. The ox
ygen and nitrogen atoms in these compounds have nonbonding electrons that can stabilize the positive c
harge of a cation through resonance forms with octets on all the atoms. Common fragmentations often cle
ave the bond ____ carbon atom bearing the oxygen or nitrogen. next to the
Loss of a small molecule is usually indicated by a fragment peak with an ___ mass number, correspondin
g to loss of an ___ mass number. even
The most common example is the loss of water from ___, which occurs so readily that the molecular ion i
s often weak or absent. alcohols
The peak corresponding to loss of water (the M–18 peak) is usually ___, however. strong
Alkenes&nbsp; "<img src=""paste-eae59353740021c4d20105c8fa795479cca32297.jpg"">"
Alkenes original molecule has a _ m/z even
Alkaenes resulting molecule has a _ m/z odd
alcohols&nbsp; "<img src=""paste-762d94c1b2d8bb80f4723107a5d6213f0161a3d0.jpg"">"
alkenes and aromatics "<img src=""paste-79979be707aebe093f0c3ec5de6f12086e6e1bbb.jpg"">"
amines&nbsp; "<img alt=""alpha"" src=""paste-45cd399a1a9a56512917758b07d5ba09843e9cb8.png"">&
nbsp;cleavage next to the carbon bearing the nitrogen to give stabilized cation&nbsp;<img src=""paste-5f
4e6aa4af92475f9302b718f7b1188e0b96fc85.jpg"">"
Ethers "lose an alkyl group<br><img src=""paste-84d82ffc67b000940debd12bef95d03a984e93bc.jpg"">"
ethers original m/z is _ resulting is _ even, odd
ketones and aldehydes "loss of alkyl groups next to the carbon bearing the oxygen to give acylium ions&n
bsp;<br><img src=""paste-bd8e24ff87342cd7b2fd06a445f12fc5637886be.jpg"">"
DEB Equation "(2(#C) + 2 -#H + #N -#X)/2"
EI bombard with electrons, lost an electron = slightly smaller mass
ESP additional proton, slighly more
turt butyl fragment 57, usually base peak
Absorption spectroscopy the measurement of the amount of light absorbed by a compound as a function
of the wavelength of light.
wave frequency "number of complete wave cycles that pass a fixed point in a second. Frequency, represe
nted by the Greek letter <span style=""color: inherit;""></span><img alt=""nu"" src=""paste-3b6e8e97e266
329940cddcf04344604ebc071093.png""> (nu), is usually given in hertz (Hz), meaning “cycles per second.
"
wavelength "Greek letter <span style=""color: inherit;""></span><img alt=""inline style lambda"" src=""past
e-d43815e828668a45f6afce92d5938dff5475271e.png""> (lambda), is the distance between any two peak
s (or any two troughs) of the wave"
wavelngth and frequency proportion "<img src=""paste-704345a475d665f5d607f7038e9fd9371ebbf1a3.jp
g"">"
photon "<img src=""paste-8705329e7be89e72766e6e8f408bacf3e10f7348.jpg"">The energy of a photon i
s proportional to its frequency and inversely proportional to its wavelength. A photon of frequency <span s
tyle=""color: inherit;""></span><img alt=""inline style nu"" src=""paste-8f9c4a78ed441ea91465b7f24fb9c9
2883bf04ce.png"">&nbsp;(or wavelength <span style=""color: inherit;""></span><img alt=""inline style lam
bda"" src=""paste-049f106cacc8925bc1b4f690d0a5aa0d3122c32a.png"">) has an energy given by"
wave number (v) proportional to number of wavelengths in a centimer&nbsp; "<img src=""paste-6646dfc5
7edcf8effbbbb001e41ec6b096f79a8e.jpg"">"
Compression on a covalent bond "<img src=""paste-b0b2bac6951f77accd6da5ea8b9be1364d462304.jpg
"">If the bond is stretched, a restoring force pulls the two atoms together toward their equilibrium bond len
gth. If the bond is compressed, the restoring force pushes the two atoms apart. If the bond is stretched or
compressed and then released, the atoms vibrate."
Heavier atoms vibrate more ____ than lighter ones&nbsp; slowly
in a group of bonds with similar bond energies, the <em>frequency (vibration) ___ with increasing atomic
weight</em>. decreases
Stronger bonds are generally stiffer, requiring more force to stretch or compress them. Thus, stronger bon
ds usually vibrate ___ than weaker bonds (assuming the atoms have similar masses) faster
O-H bonds are ___ than C-H bonds, so O-H bonds vibrate at ___ frequencies stronger, faster&nbsp;
triple bonds are ___ than double bonds and vibrate at ___ frequencies stronger, faster
as bond strength increases, vibration frequency ___ ___increases&nbsp;
Vibrational modes of water: symetric stretching, antisymmetric stretching, bending (scissoring) "<img src=
""paste-5358468e3b5f626d5cb11c9c7e80be97b81867bb.jpg"">"
How many modes do atoms have?&nbsp; "A nonlinear molecule with <em>n</em> atoms generally has
<span style=""color: inherit;""></span><img alt=""inline style 3 n minus 6"" src=""paste-3b99bf708887d1a
ef8d0173716ecc7ca5a309091.png""> fundamental vibrational modes."
What is the key to IR active vibration?&nbsp; "<i>the vibration must change the dipole moment of the mol
ecule.&nbsp;</i>For example, he triple bond of acetylene <span style=""color: inherit;""></span><img alt=
""inline style open parentheses straight H back space minus back space straight C back space identical to
back space straight C back space minus back space straight H close parentheses"" src=""paste-5c32745
f5c1fd0e7ee545521ddac5dd7eaf8c957.png"">&nbsp;has zero dipole moment, and the dipole moment re
mains zero if the bond is stretched or compressed. Because the vibration produces no change in the dipol
e moment, there is no absorption of energy. This vibration is said to be <a href=""about:blank#"">IR-inacti
ve</a>, and it produces no absorption in the IR spectrum."
infrared spectrum of n-octane,&nbsp;<b>four major absorption band</b> "broad band between&nbsp;<sp
an style=""color: inherit;""></span><img alt=""2800"" src=""paste-1a0eb97c60ba3f7f51019f83c01d30e899
daac67.png""> and <span style=""color: inherit;""></span><img alt=""3000 ? cm to the power of negative
1 end exponent"" src=""paste-975d407070b9164369e47c4eb500d6a3f4f06306.png""> results from <span
style=""color: inherit;""></span><img alt=""straight C back space minus back space straight H"" src=""pas
te-5152a0e85e7d1527264faff958ca9cf3af721c3e.png"">&nbsp;stretching vibrations, and the band at <sp
an style=""color: inherit;""></span><img alt=""1467 ? cm to the power of negative 1 end exponent"" src=""
paste-3bf33a6945b9b412395707b06d87730dd4a80c71.png""> results from a scissoring vibration of the <
span style=""color: inherit;""></span><img alt=""CH subscript 2"" src=""paste-94f42ccabddf9d4f8bbec3a6
6117f96a6bcff4dd.png"">&nbsp;groups. The absorptions at 1378 and <span style=""color: inherit;""></sp
an><img alt=""722 ? cm to the power of negative 1 end exponent"" src=""paste-e0f5d011c244199db903b
dfbf030b76109245360.png""> result from the bending vibrations (rocking) of <span style=""color: inherit;""
></span><img alt=""CH subscript 3"" src=""paste-d1cd9fdcdc01d9d874e341b64d02d51bca70bcf8.png"">
&nbsp;and <span style=""color: inherit;""></span><img alt=""C H subscript 2 end subscript"" src=""paste0f05425324adba8215f20654762d90257daa1610.png""> groups, respectively. Because most organic com
pounds contain at least some saturated <span style=""color: inherit;""></span><img alt=""straight C back
space minus back space straight H"" src=""paste-5152a0e85e7d1527264faff958ca9cf3af721c3e.png"">&
nbsp;bonds and some <span style=""color: inherit;""></span><img alt=""CH subscript 2"" src=""paste-94f
42ccabddf9d4f8bbec3a66117f96a6bcff4dd.png""> and <span style=""color: inherit;""></span><img alt=""
CH subscript 3"" src=""paste-d1cd9fdcdc01d9d874e341b64d02d51bca70bcf8.png"">&nbsp;groups, all th
ese bands are common"
C-C band 1200 cm
C-H 2800 - 3000
CH2 1467
Carbon carbon bond streatching frequencies c-c 1200, c = c 1660 c =_ c greater than 2200
conjugated&nbsp; two double bonds are one bond apart
what is significant about conjugate bonds? "conjugated double bonds are slightly more stable than isolate
d double bonds because there is a small amount of pi bonding between them. This overlap between the p
i bonds leaves a little less electron density in the double bonds themselves. As a result, they are a little le
ss stiff and vibrate a little more slowly than an isolated double bond. Isolated double bonds absorb around
1640&nbsp;to <span style=""color: inherit;""></span><img alt=""inline style 1680 thin space straight c str
aight m to the power of negative 1 end exponent comma"" src=""paste-096848d33467c0b2a23d941fb8e9
da38ae49254c.png""> while conjugated double bonds absorb around 1620 to&nbsp;<span style=""color: i
nherit;""></span><img alt=""inline style 1640 thin space straight c straight m to the power of negative 1 en
d exponent."" src=""paste-c911530fa0c3ee23cc58f8334e89b03939b5b9d5.png"">"
What is true about the stretching absorption of an internal alkyne? may be weak or absent, however, beca
use of the symmetry of the disubstituted triple bond with a very small or zero dipole moment.
Carbon-hydrogen bonds with SP3 hybrid:&nbsp; "generally absorb at frequencies just below (to the right
of) &nbsp;<span style=""color: inherit;""></span><img alt=""3000 space cm to the power of negative 1 en
d exponent"" src=""paste-0b5ab6fff86b2a4032f9d42319db93b0f1edce57.png"">"
Carbon-hydrogen bonds with SP2 hybrid:&nbsp; "absorb just above (to the left of) <span style=""color: inh
erit;""></span><img alt=""3000 space cm to the power of negative 1 end exponent"" src=""paste-0b5ab6ff
f86b2a4032f9d42319db93b0f1edce57.png"">."
Why is there a difference between SP2 and SP3 hybrid conjugations?&nbsp; "the amount of s character i
n the carbon orbital used to form the bond. The s orbital is closer to the nucleus than the p orbitals, and st
ronger, stiffer bonds result from orbitals with more s character. Even if an alkene’s <span style=""color: in
herit;""></span><img alt=""inline style straight C back space equals back space straight C"" src=""paste-8
13e0ccc0991dc586acb7fa7783c003f39b53fd6.png""> absorption is weak or absent, the unsaturated <spa
n style=""color: inherit;""></span><img alt=""inline style straight C back space minus back space straight
H"" src=""paste-dc9ea699b8f8f9672ffbcf0807b2aadc4ceb1208.png""> stretch above&nbsp; <span style="
"color: inherit;""></span><img alt=""3000 space cm to the power of negative 1 end exponent"" src=""paste
-0b5ab6fff86b2a4032f9d42319db93b0f1edce57.png"">&nbsp;reveals the presence of the double bond. A
n <span style=""color: inherit;""></span><img alt=""s p cubed"" src=""paste-69ddec5625c51792c8420363
f050d88c058522ac.png""> orbital is one-fourth s character, and an <span style=""color: inherit;""></span>
<img alt=""s p squared"" src=""paste-870c7781a95b576be30d532fc1d0cd7727d70d48.png""> orbital is o
ne-third s character. We expect the bond using the <span style=""color: inherit;""></span><img alt=""s p s
quared"" src=""paste-870c7781a95b576be30d532fc1d0cd7727d70d48.png""> orbital to be slightly strong
er, with a higher vibration frequency. The <span style=""color: inherit;""></span><img alt=""inline style str
aight C back space minus back space straight H"" src=""paste-dc9ea699b8f8f9672ffbcf0807b2aadc4ceb1
208.png"">&nbsp;bond of a terminal alkyne is formed using an <em>sp</em> hybrid orbital, with about o
ne-half <em>s</em> character. This bond is stiffer than a <span style=""color: inherit;""></span><img alt=
""inline style straight C back space minus back space straight H"" src=""paste-dc9ea699b8f8f9672ffbcf08
07b2aadc4ceb1208.png"">&nbsp;bond using an <span style=""color: inherit;""></span><img alt=""s p cub
ed"" src=""paste-69ddec5625c51792c8420363f050d88c058522ac.png""> or <span style=""color: inherit;""
></span><img alt=""s p squared"" src=""paste-870c7781a95b576be30d532fc1d0cd7727d70d48.png""> h
ybrid carbon, and it absorbs at a higher frequency: about <span style=""color: inherit;""></span><img alt="
"Error converting from MathML to accessible text."" src=""paste-9ef8e15ff42eb7ff999b1a4b8a71e2b4ee3
50879.png"">"
C-H bond strengthening frequencies "<img src=""paste-c7fcadb894b51dedf47f98a86be9e50d962bf7f4.jp
g"">"
"The <span style=""color: inherit;""></span><img alt=""begin inline style straight O back space minus bac
k space straight H end style"" src=""paste-68b74efbbf7056cea195c02d0575a7205cf96dc4.png""> bonds
of alcohols and the <span style=""color: inherit;""></span><img alt=""begin inline style straight N back spa
ce minus back space straight H end style"" src=""paste-eebcbca78968f6e61d52b6492fbaae8ae0736662.
png""> bonds of amines are ___ The vibration frequencies of <span style=""color: inherit;""></span><img
alt=""begin inline style straight O back space minus back space straight H end style"" src=""paste-68b74ef
bbf7056cea195c02d0575a7205cf96dc4.png""> and <span style=""color: inherit;""></span><img alt=""begi
n inline style straight N back space minus back space straight H end style"" src=""paste-eebcbca78968f6
e61d52b6492fbaae8ae0736662.png""> bonds therefore occur at ___ frequencies than those of most <sp
an style=""color: inherit;""></span><img alt=""begin inline style straight C back space minus back space st
raight H end style"" src=""paste-47f09965cb4b27fe31f90a29c36b600066066e78.png"">&nbsp;bonds (exc
ept for alkynyl <span style=""color: inherit;""></span><img alt=""identical to back space straight C back sp
ace minus back space straight H"" src=""paste-0cfa351fe24290e2349b50256fc626efbc0343f0.png""> bon
ds).&nbsp;<div><div></div></div>" strong, higher
What is the stretching frequency of alcohol O-H 3300 cm
What is the stretching frequency of O-H in an acid 3000 broad
what is the stretching frequency of amine N-H 3300, broad with spike
c=o has a _ dipole moment, so it produces _ infrared stretching absorptions at around _ large, intense 17
00
simple ketones and carboxylix acids 1710
c = bonds in ketone aldeyde and acid "<img src=""paste-fd3ef5a25f3a4f593a818d8085839da1a8a4d6ea.j
pg"">"
C-N single bond 1200
stronger bond = ___ number bigger number (remember inverse fraction tho!!!)
General summary "<img src=""paste-9cf20b2b2393115a4fd054c6e4f7d3daec38ed6d.jpg"">"