ir peaks of cyclohexene

Advanced Organic Chemistry: Infrared spectrum of cyclohexene cyclo C 6 H 10

Interpreting the i nfrared spectrum of cyclohexene

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Infrared spectroscopy - spectra index

Introductory note on the infrared spectrum of cyclohexene

Students and teachers please note my explanation of the infrared spectrum of cyclohexene is designed for advanced, but pre-university, chemistry courses . Based in the infrared spectrum diagram for cyclohexene, only some of the most prominent peaks for particular bond vibrations are discussed, particularly if cyclohexene has a functional group with a particular characteristic wavenumber peak. The infrared spectrum of cyclohexene is unique and the whole, or selected wavenumbers, can be used to fingerprint its identity, sometimes analysing a mixture containing cyclohexene or following its change of concentration in a reaction.

Spectra obtained from a liquid film of cyclohexene. The right-hand part of the of the infrared spectrum of cyclohexene, wavenumbers ~1500 to 400 cm -1 is considered the fingerprint region for the identification of cyclohexene and most organic compounds. It is due to a unique set of complex overlapping vibrations of the atoms of the molecule of cyclohexene.

aliphatic cyclohexene , ,  , 

Interpretation of the infrared spectrum of cyclohexene The most prominent infrared absorption lines of cyclohexene Multiple C-H stretching vibration absorption lines peaking at ~3100 to 2950 cm -1 . The very characteristic absorption peaking at ~1640 cm -1 for C=C stretching vibrations, typical of an aliphatic alkene molecule. (I have seen the 1440 cm -1 absorption peak attributed to C=C vibrations, but this does not fit in with most spectral data of aliphatic alkenes that I've come across which attributes this to CH 2 bending vibrations). Most of the peaks in the fingerprint region are due to C-H vibrations of some origin e.g. from alkyl CH 2 , C-H and =C-H groupings.

The absence of other specific functional group bands will show that a particular functional group is absent from the cyclohexene molecular structure.

Key words & phrases: isomer of molecular formula C6H10 image and diagram explaining the infrared spectrum of cyclohexene, complete infrared absorption spectrum of cyclohexene, comparative spectra of cyclohexene, prominent peaks/troughs for identifying functional groups in the infrared spectrum of cyclohexene, important wavenumber values in cm-1 for peaks/troughs in the infrared spectrum of cyclohexene, revision of infrared spectroscopy of cyclohexene, fingerprint region analysis of cyclohexene, how to identify cyclohexene from its infrared spectrum, identifying organic compounds like cyclohexene from their infrared spectrum, how to analyse the absorption bands in the infrared spectrum of cyclohexene detection of alkene functional groups in the cyclohexene molecule example of the infrared spectrum of a molecule like cyclohexene with a alkene functional group  interpreting interpretation of the infrared spectrum of cyclohexene shows presence of alkene functional group How do you interpret the infrared absorption spectrum of cyclohexene How to interpret the infrared spectrum of cyclohexene Explanatory diagram of the infrared spectrum of the cyclohexene molecule in terms of its molecular structure. Listing data of the prominent main wavenumber peaks troughs in the infrared spectrum of cyclohexene. How to explain the infrared spectrum of cyclohexene. Use of the infrared spectrum of cyclohexene, identification of cyclohexene from its infrared spectrum - fingerprint wavenumber pattern to identify the cyclohexene molecule. The uses of the infrared spectrum of the cyclohexene molecule. The distinctive features of the infrared spectrum of the cyclohexene molecule explained. explaining the peaks-trough of the transmittance of the infrared spectrum of cyclohexene what does the infrared spectrum tell you about the structure and properties of the cyclohexene molecule? How do you interpret the infrared absorption spectrum of cyclohexene How to interpret the infrared spectrum of cyclohexene Explanatory diagram of the infrared spectrum of the cyclohexene molecule in terms of its molecular structure. Listing data of the prominent main wavenumber peaks troughs in the infrared spectrum of cyclohexene. How to explain the infrared spectrum of cyclohexene. Use of the infrared spectrum of cyclohexene, identification of cyclohexene from its infrared spectrum - fingerprint wavenumber pattern to identify the cyclohexene molecule. The uses of the infrared spectrum of the cyclohexene molecule. The distinctive features of the infrared spectrum of the cyclohexene molecule explained interpretation diagram explaining the peaks-trough of the transmittance of the infrared spectrum of cyclohexene what does the infrared spectrum tell you about the structure and properties of the cyclohexene molecule? How is infrared spectrum of cyclohexene used to identify cyclohexene?

The mass spectrum of cyclohexene

The H-1 NMR spectrum of cyclohexene

The C-13 NMR spectrum of cyclohexene

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12.8 Infrared Spectra of Some Common Functional Groups

12.8 • Infrared Spectra of Some Common Functional Groups

As each functional group is discussed in future chapters, the spectroscopic properties of that group will be described. For the present, we’ll point out some distinguishing features of the hydrocarbon functional groups already studied and briefly preview some other common functional groups. We should also point out, however, that in addition to interpreting absorptions that are present in an IR spectrum, it’s also possible to get structural information by noticing which absorptions are not present. If the spectrum of a compound has no absorptions at 3300 and 2150 cm –1 , the compound is not a terminal alkyne; if the spectrum has no absorption near 3400 cm –1 , the compound is not an alcohol; and so on.

The IR spectrum of an alkane is fairly uninformative because no functional groups are present and all absorptions are due to C–H and C–C bonds. Alkane C–H bonds show a strong absorption from 2850 to 2960 cm –1 , and saturated C–C bonds show a number of bands in the 800 to 1300 cm –1 range. Since most organic compounds contain saturated alkane-like portions, most organic compounds have these characteristic IR absorptions. The C–H and C–C bands are clearly visible in the three spectra shown previously in Figure 12.21 .

Alkenes show several characteristic stretching absorptions. Vinylic =C–H bonds absorb from 3020 to 3100 cm –1 , and alkene C═C C═C bonds usually absorb near 1650 cm –1 , although in some cases their peaks can be rather small and difficult to see clearly when the alkene is symmetric, or nearly so. Both absorptions are visible in the 1-hexene spectrum in Figure 12.21 b.

Alkenes have characteristic =C–H out-of-plane bending absorptions in the 700 to 1000 cm –1 range, thereby allowing the substitution pattern on a double bond to be determined ( Figure 12.23 ). For example, monosubstituted alkenes such as 1-hexene show strong characteristic bands at 910 and 990 cm –1 , and 1,1-disubstituted alkenes ( R 2 C═ CH 2 R 2 C═ CH 2 ) have an intense band at 890 cm –1 .

Alkynes show a C≡C C≡C stretching absorption at 2100 to 2260 cm –1 , an absorption that is much more intense for terminal alkynes than for internal alkynes. Terminal alkynes such as 1-hexyne also have a characteristic ≡C–H ≡C–H stretching absorption at 3300 cm –1 ( Figure 12.21 c). This band is diagnostic for terminal alkynes because it is fairly intense and quite sharp.

Aromatic Compounds

Aromatic compounds, such as benzene, have a weak C–H stretching absorption at 3030 cm –1 , just to the left of a typical saturated C–H band. In addition, they have a series of weak absorptions in the 1660 to 2000 cm –1 range and a series of medium-intensity absorptions in the 1450 to 1600 cm –1 region. These latter absorptions are due to complex molecular motions of the entire ring. The C–H out-of-plane bending region for benzene derivatives, between 650 to 1000 cm –1 , gives valuable information about the ring’s substitution pattern, as it does for the substitution pattern of alkenes ( Figure 12.24 ).

The IR spectrum of phenylacetylene, shown in Figure 12.29 at the end of this section, gives an example, clearly showing the following absorbances: ≡C–H ≡C–H stretch at 3300 cm –1 , C–H stretches from the benzene ring at 3000 to 3100 cm –1 , C═C C═C stretches of the benzene ring between 1450 and 1600 cm –1 , and out-of-plane bending of the ring’s C–H groups, indicating monosubstitution at 750 cm –1 .

The O–H functional group of alcohols is easy to spot. Alcohols have a characteristic band in the range 3400 to 3650 cm –1 that is usually broad and intense. Hydrogen bonding between O–H groups is responsible for making the absorbance so broad. If an O–H stretch is present, it’s hard to miss this band or to confuse it with anything else.

Cyclohexanol ( Figure 12.25 ) is a good example.

The N–H functional group of amines is also easy to spot in the IR, with a characteristic absorption in the 3300 to 3500 cm –1 range. Although alcohols absorb in the same range, an N–H absorption band is much sharper and less intense than an O–H band.

Primary amines (R–NH 2 ) have two absorbances—one for the symmetric stretching mode and one for the asymmetric mode ( Figure 12.26 ). Secondary amines (R 2 N–H) only have one N–H stretching absorbance in this region.

Carbonyl Compounds

Carbonyl functional groups are the easiest to identify of all IR absorptions because of their sharp, intense peak in the range 1670 to 1780 cm –1 . Most important, the exact position of absorption within this range can often be used to identify the exact kind of carbonyl functional group—aldehyde, ketone, ester, and so forth.

Saturated aldehydes absorb at 1730 cm –1 ; aldehydes next to either a double bond or an aromatic ring absorb at 1705 cm –1 .

The C–H group attached to the carbonyl is responsible for the characteristic IR absorbance for aldehydes at 2750 and 2850 cm –1 ( Figure 12.27 ). Although these are not very intense, the absorbance at 2750 cm –1 is helpful when trying to distinguish between an aldehyde and a ketone.

Saturated open-chain ketones and six-membered cyclic ketones absorb at 1715 cm –1 . Ring strain stiffens the C═O C═O bond, making five-membered cyclic ketones absorb at 1750 cm –1 and four-membered cyclic ketones absorb at 1780 cm –1 , about 20 to 30 cm –1 lower than the corresponding saturated ketone.

Saturated esters have a C═O C═O absorbance at 1735 cm –1 and two strong absorbances in the 1300 to 1000 cm –1 range from the C–O portion of the functional group. Like other carbonyl functional groups, esters next to either an aromatic ring or a double bond absorb at 1715 cm –1 , about 20 to 30 cm –1 lower than a saturated ester.

Worked Example 12.5

Predicting ir absorptions of compounds.

Where might the following compounds have IR absorptions?

(b) Absorptions: 3300 cm –1 ( ≡C–H ≡C–H ), 2100 to 2260 cm –1 ( C≡C C≡C ), 1735 cm –1 ( C═O C═O ). This molecule has a terminal alkyne triple bond and a saturated ester carbonyl group.

Worked Example 12.6

Identifying functional groups from an ir spectrum.

The IR spectrum of an unknown compound is shown in Figure 12.28 . What functional groups does the compound contain?

The IR spectrum of phenylacetylene is shown in Figure 12.29. What absorption bands can you identify?

Where might the following compound have IR absorptions?

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Organic chemistry

Course: organic chemistry   >   unit 14.

• Introduction to infrared spectroscopy
• Bonds as springs
• Signal characteristics - wavenumber
• IR spectra for hydrocarbons
• Signal characteristics - intensity
• Signal characteristics - shape
• Symmetric and asymmetric stretching
• IR signals for carbonyl compounds

IR spectra practice

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11.5: Infrared Spectra of Some Common Functional Groups

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Common Group Frequencies Summary

When analyzing an IR spectrum, it is helpful to overlay the diagram below onto the spectrum with our mind to help recognize functional groups.

The region of the infrared spectrum from 1200 to 700 cm -1 is called the fingerprint region. This region is notable for the large number of infrared bands that are found there. Many different vibrations, including C-O, C-C and C-N single bond stretches, C-H bending vibrations, and some bands due to benzene rings are found in this region. The fingerprint region is often the most complex and confusing region to interpret, and is usually the last section of a spectrum to be interpreted. However, the utility of the fingerprint region is that the many bands there provide a fingerprint for a molecule.

Group Frequencies - a closer look

Detailed information about the infrared absorptions observed for various bonded atoms and groups is usually presented in tabular form. The following table provides a collection of such data for the most common functional groups. Following the color scheme of the chart, stretching absorptions are listed in the blue-shaded section and bending absorptions in the green shaded part. More detailed descriptions for certain groups (e.g. alkenes, arenes, alcohols, amines & carbonyl compounds) may be viewed by clicking on the functional class name . Since most organic compounds have C-H bonds, a useful rule is that absorption in the 2850 to 3000 cm -1 is due to sp 3 C-H stretching; whereas, absorption above 3000 cm -1 is from sp 2 C-H stretching or sp C-H stretching if it is near 3300 cm -1 .

Recognizing Group Frequencies in IR Spectra - a very close look

Hydrocarbons.

Hydrocarbons compounds contain only C-H and C-C bonds, but there is plenty of information to be obtained from the infrared spectra arising from C-H stretching and C-H bending.

In alkanes, which have very few bands, each band in the spectrum can be assigned:

• C–H stretch from 3000–2850 cm -1
• C–H bend or scissoring from 1470-1450 cm -1
• C–H rock, methyl from 1370-1350 cm -1
• C–H rock, methyl, seen only in long chain alkanes, from 725-720 cm -1

Figure 3. shows the IR spectrum of octane. Since most organic compounds have these features, these C-H vibrations are usually not noted when interpreting a routine IR spectrum. Note that the change in dipole moment with respect to distance for the C-H stretching is greater than that for others shown, which is why the C-H stretch band is the more intense.

In alkenes compounds, each band in the spectrum can be assigned:

• C=C stretch from 1680-1640 cm -1
• =C–H stretch from 3100-3000 cm -1
• =C–H bend from 1000-650 cm -1

Figure 4. shows the IR spectrum of 1-octene. As alkanes compounds, these bands are not specific and are generally not noted because they are present in almost all organic molecules.

In alkynes, each band in the spectrum can be assigned:

• –C?C– stretch from 2260-2100 cm -1
• –C?C–H: C–H stretch from 3330-3270 cm -1
• –C?C–H: C–H bend from 700-610 cm -1

The spectrum of 1-hexyne, a terminal alkyne, is shown below.

In aromatic compounds, each band in the spectrum can be assigned:

• C–H stretch from 3100-3000 cm -1
• overtones, weak, from 2000-1665 cm -1
• C–C stretch (in-ring) from 1600-1585 cm -1
• C–C stretch (in-ring) from 1500-1400 cm -1
• C–H "oop" from 900-675 cm -1

Note that this is at slightly higher frequency than is the –C–H stretch in alkanes. This is a very useful tool for interpreting IR spectra. Only alkenes and aromatics show a C–H stretch slightly higher than 3000 cm -1 .

Figure 6. shows the spectrum of toluene.

Functional Groups Containing the C-O Bond

Alcohols have IR absorptions associated with both the O-H and the C-O stretching vibrations.

• O–H stretch, hydrogen bonded 3500-3200 cm -1
• C–O stretch 1260-1050 cm -1 (s)

Figure 7. shows the spectrum of ethanol. Note the very broad, strong band of the O–H stretch.

The carbonyl stretching vibration band C=O of saturated aliphatic ketones appears:

• C=O stretch - aliphatic ketones 1715 cm -1

- ?, ?-unsaturated ketones 1685-1666 cm -1

Figure 8. shows the spectrum of 2-butanone. This is a saturated ketone, and the C=O band appears at 1715.

If a compound is suspected to be an aldehyde, a peak always appears around 2720 cm -1 which often appears as a shoulder-type peak just to the right of the alkyl C–H stretches.

• H–C=O stretch 2830-2695 cm -1
• aliphatic aldehydes 1740-1720 cm -1
• alpha, beta-unsaturated aldehydes 1710-1685 cm -1

Figure 9. shows the spectrum of butyraldehyde.

The carbonyl stretch C=O of esters appears:

• aliphatic from 1750-1735 cm -1
• ?, ?-unsaturated from 1730-1715 cm -1
• C–O stretch from 1300-1000 cm -1

Figure 10. shows the spectrum of ethyl benzoate.

The carbonyl stretch C=O of a carboxylic acid appears as an intense band from 1760-1690 cm -1 . The exact position of this broad band depends on whether the carboxylic acid is saturated or unsaturated, dimerized, or has internal hydrogen bonding.

• O–H stretch from 3300-2500 cm -1
• C=O stretch from 1760-1690 cm -1
• C–O stretch from 1320-1210 cm -1
• O–H bend from 1440-1395 and 950-910 cm -1

Figure 11. shows the spectrum of hexanoic acid.

Organic Nitrogen Compounds

• N–O asymmetric stretch from 1550-1475 cm -1
• N–O symmetric stretch from 1360-1290 cm -1

Organic Compounds Containing Halogens

Alkyl halides are compounds that have a C–X bond, where X is a halogen: bromine, chlorine, fluorene, or iodine.

• C–H wag (-CH 2 X) from 1300-1150 cm -1
• C–Cl stretch 850-550 cm -1
• C–Br stretch 690-515 cm -1

The spectrum of 1-chloro-2-methylpropane are shown below.

For more Infrared spectra Spectral database of organic molecules is introduced to use free database. Also, the infrared spectroscopy correlation table is linked on bottom of page to find other assigned IR peaks.

1. What functional groups give the following signals in an IR spectrum?

A) 1700 cm -1

B) 1550 cm -1

C) 1700 cm -1 and 2510-3000 cm -1

2. How can you distinguish the following pairs of compounds through IR analysis?

A) CH 3 OH (Methanol) and CH 3 CH 2 OCH 2 CH 3 (Diethylether)

B) Cyclopentane and 1-pentene.

3. The following spectra is for the accompanying compound. What are the peaks that you can I identify in the spectrum?

Source: SDBSWeb : http://sdbs.db.aist.go.jp (National Institute of Advanced Industrial Science and Technology, 2 December 2016)

4. What absorptions would the following compounds have in an IR spectra?

A) A OH peak will be present around 3300 cm -1 for methanol and will be absent in the ether.

B) 1-pentene will have a alkene peak around 1650 cm -1 for the C=C and there will be another peak around 3100 cm -1 for the sp 2 C-H group on the alkene

C) Cannot distinguish these two isomers. They both have the same functional groups and therefore would have the same peaks on an IR spectra.

Frequency (cm-1) Functional Group

3200 C≡C-H

2900-3000 C-C-H, C=C-H

2100 C≡C

(There is also an aromatic undertone region between 2000-1600 which describes the substitution on the phenyl ring.)

3300 (broad) O-H

2000-1800 Aromatic Overtones

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William Reusch, Professor Emeritus ( Michigan State U. ), Virtual Textbook of Organic Chemistry

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Cyclohexane

• Formula : C 6 H 12
• Molecular weight : 84.1595

• IUPAC Standard InChIKey: XDTMQSROBMDMFD-UHFFFAOYSA-N Copy
• CAS Registry Number: 110-82-7

• Cyclohexane, d12
• Cyclohexane-d12
• Cyclohexane-1,2,3-d6
• Hephane-d16
• Other names: Benzene, hexahydro-; Hexahydrobenzene; Hexamethylene; Hexanaphthene; Cicloesano; Cykloheksan; Rcra waste number U056; UN 1145; NSC 406835
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Infrared Spectrum

• Gas phase thermochemistry data
• Condensed phase thermochemistry data
• Phase change data
• Reaction thermochemistry data
• Henry's Law data
• Gas phase ion energetics data
• Ion clustering data
• IR Spectrum
• Mass spectrum (electron ionization)
• UV/Visible spectrum
• Vibrational and/or electronic energy levels
• Gas Chromatography
• Fluid Properties
• Computational Chemistry Comparison and Benchmark Database
• Gas Phase Kinetics Database
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Data compiled by: Coblentz Society, Inc.

Condensed Phase Spectrum

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Additional Data

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• Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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