Alkanes and Cycloalkanes

The infrared spectra of the alkanes show clearly absorptions corresponding to the C−HC−H stretching frequencies at 2850cm−1 to 3000cm−1. The C−C stretching absorptions have variable frequencies and are usually weak. Methyl (CH3−) and methylene (−CH2−) groups normally have characteristic C−H bending vibrations at 1400cm−1 to 1470cm−1. Methyl groups also show a weaker band near 1380cm−1. Two sample infrared spectra that illustrate these features are given in Figure 9-11.

The infrared spectra of the cycloalkanes are similar to those of the alkanes, except that when there are no alkyl substituents the characteristic

Figure 9-11: Infrared spectra of (a) octane and (b) 2,2,4-trimethylpentane as pure liquids. Notice the C−H stretching around 2900cm−1 and C−H bending frequency around 1460cm−1. The bands near 1370cm−1 for 2,2,4-trimethylpentane are characteristic of methyl C−H bending frequencies.

bending frequencies of methyl groups at 1380cm−1 are absent. A moderately strong CH2 "scissoring" frequency is observed between 1440cm−1 and 1470cm−1, the position depending somewhat on the size of the ring. These features of the infrared spectra of cycloalkanes are illustrated in Figure 9-12 using cyclooctane and methylcyclohexane as examples.

Figure 9-11.

مواضيع ذات صلة

مركبات الآزو متجانسة الحلقة Homocyclic azo compounds

تصنيف مركبات الآزو Classification of azo compound

أصباغ الآزو Azo Dye

تفاعلات الازدواج Reaction Coupling

أملاح الدايازونيوم الاروماتية      Aromtic Diazonium Salt    

أهمية الكواشف العضوية reagents Importance of organic

الثايوزبينات Thiazepines

الدايازبينات Diazepines

الاوكسازبينات Oxazepines

المركبات الحلقية غير المتجانسة Heterocyclic Compounds

نبذة عن مظاهر كيمياء الكلورامين-T الحيوية واهميته

بعض مظاهر كيمياء الكلورامين-T