Organic Chemistry

Synthesis of Ethers – In this topic, we will discuss 6 methods for Synthesis of Ethers as follows: 1. Ethers by Intermolecular Dehydration of Alcohols – Two alcohol molecules can form an ether by loss of water through an acid-catalyzed substitution reaction. – This reaction competes with the formation of …

– In this topic, we will discuss the Williamson Ether Synthesis : Mechanism, Examples and Solved problems. Williamson Ether Synthesis – We have already seen most of the common methods for synthesizing ethers. – We review them at this time, looking more closely at the mechanisms to see which methods …

Spectroscopy of Ethers – Here we will discuss Spectroscopy of Ethers: IR Spectroscopy, Mass Spectroscopy, 13C NMR amd 1H NMR.  Infrared Spectroscopy of Ethers – Infrared spectra do not show obvious or reliable absorptions for ethers. – Most ethers give a moderate to strong C-O stretch around 1000 to 1200 …

Nomenclature of Ethers – We have been using the common nomenclature of ethers, which is sometimes called the alkyl alkyl ether system. – The IUPAC system, generally used with more complicated ethers, is sometimes called the alkoxy alkane system. – Common names are almost always used for simple ethers. Common …

– In this topic, we will discuss The Physical Properties of Ethers. Introduction to Ethers  – Ethers are compounds of formula R-O-R’ where R and R’ may be alkyl groups or aryl (benzene ring) groups. – Like alcohols, ethers are related to water, with alkyl groups replacing the hydrogen atoms. …

– In this topic, we will discuss some Essential Terms in NMR spectroscopy. Essential Terms in NMR spectroscopy accidentally equivalent nuclei – Nuclei that are not chemically equivalent, yet absorb at nearly the same chemical shift and are not resolved. – Nuclei that absorb at the same chemical shift cannot …

– In this topic, we will discuss Nuclear Magnetic Resonance Imaging. Nuclear magnetic resonance imaging – When chemists use NMR spectroscopy, they take great pains to get the most uniform magnetic field possible (often homogeneous to within one part per billion). – They place small tubes of homogeneous solutions in …

Interpreting Carbon NMR Spectra – Interpreting Carbon NMR Spectra (13C NMR spectra) uses the same principles as interpreting 1H NMR spectra. – In fact, carbon spectra are often easier to interpret. – The 13C NMR spectrum provides the following information: (1) The number of different signals implies how many different …

– In this topic, we will discuss The Carbon-13 NMR Spectroscopy. Carbon-13 NMR Spectroscopy – Where does a carbonyl group absorb in the NMR? Where does an internal alkyne absorb? – In the proton NMR, both of these groups are invisible. Sometimes we can infer their presence: If the carbonyl …

– In this topic, we will discuss The Time Dependence of NMR Spectroscopy. Time Dependence of NMR Spectroscopy – We have already seen evidence that NMR does not provide an instantaneous picture of a molecule. – For example, a terminal alkyne does not give a spectrum where the molecules oriented …

– In the this topic we talk about Stereochemical Nonequivalence of Protons in NMR Spectroscopy. Stereochemical Nonequivalence of Protons – Stereochemical differences often result in different chemical shifts for protons on the same carbon atom. – For example, the two protons on C1 of allyl bromide (3-bromopropene) are not equivalent. …

– In the last topic we talk about Spin-Spin Splitting in ¹H NMR Spectra, but In this topic, we will discuss The Complex Splitting. Complex Splitting in ¹H NMR Spectra – There are many cases of complex splitting, where signals are split by adjacent protons of more than one type, …

– In this topic, we will discuss The Spin-Spin Splitting in ¹H NMR Spectra. Theory of Spin-Spin Splitting – A proton in the NMR spectrometer is subjected to both the external magnetic field and the induced field of the shielding electrons. – If there are other protons nearby, their small …

– In this topic, we will discuss The Areas of the Peaks in NMR Spectroscopy Areas of the Peaks – The area under a peak is proportional to the number of hydrogens contributing to that peak. – For example, in the methyl tert-butyl ether spectrum (Figure 1), the absorption of …

The Number of Signals – In general, the number of NMR signals corresponds to the number of different kinds of protons present in the molecule. – For example, methyl tert-butyl ether has two types of protons (Figure 1). – The three methoxy protons are chemically identical, and they give rise …

– In this topic, we will discuss the Chemical Shift in 1H NMR Spectroscopy. What is Chemical Shift? – The variations in the positions of NMR absorptions, arising from electronic shielding and deshielding, are called chemical shifts. – Chemical shift is The difference (in parts per million) between the resonance …

– In this topic, we will discuss the Fragmentation Patterns in Mass Spectrometry. Fragmentation Patterns in Mass Spectrometry – In addition to the molecular formula, the mass spectrum provides structural information. – An electron with a typical energy of 70 eV (6740 kJ mol or 1610 kcal mol) has far …

Determination of the Molecular Formula by Mass Spectrometry – we can Determine the Molecular Formula by Mass Spectrometry and we will discuss : (A) High-Resolution Mass Spectrometry (B) Use of Heavier Isotope Peaks (A) High-Resolution Mass Spectrometry – Although mass spectra usually show the particle masses rounded to the nearest …

Mass spectrometry (MS) provides the molecular weight and valuable information about the molecular formula, using a very small sample. Introduction to Mass Spectrometry – Infrared spectroscopy gives information about the functional groups in a molecule, but it tells little about the size of the molecule or what heteroatoms are present. …

– In this subject, we will talk about Characteristic Absorptions of Carbonyl Compounds such as Ketones, Aldehydes, Amines, and Acids. Characteristic Absorptions of Carbonyl Compounds – Because it has a large dipole moment, the C=O double bond produces intense infrared stretching absorptions. – Carbonyl groups absorb at frequencies around 1700 …