The document discusses UV spectroscopy and the different types of bands that can be observed. It explains that compounds with higher conjugation absorb at lower wavelengths due to a smaller energy gap between orbitals. Four main bands are described: K-band observed in conjugated double bonds with high intensity; R-band in carbonyl compounds with low intensity as it is a forbidden transition; B-band in aromatic/heteroaromatic compounds typically between 230-270nm; and E-band in benzenoid systems where benzene shows a strong band at 184nm.
The document discusses UV spectroscopy and the different types of bands that can be observed. It explains that compounds with higher conjugation absorb at lower wavelengths due to a smaller energy gap between orbitals. Four main bands are described: K-band observed in conjugated double bonds with high intensity; R-band in carbonyl compounds with low intensity as it is a forbidden transition; B-band in aromatic/heteroaromatic compounds typically between 230-270nm; and E-band in benzenoid systems where benzene shows a strong band at 184nm.
This document discusses ultraviolet-visible (UV-Vis) spectroscopy. It begins by defining spectroscopy and describing the electromagnetic radiation spectrum. It then focuses on UV-Vis spectroscopy, explaining that it involves electronic transitions in molecules caused by the absorption of ultraviolet or visible light. The major electronic transitions that can occur are defined, including σ → σ*, n → σ*, π → π*, and n → π* transitions. Factors that affect these transitions, such as conjugation, are also discussed. Real-world examples of molecular structures and the transitions they undergo are provided.
The document discusses various spectroscopic methods used in organic chemistry including UV-Visible, Infrared, Nuclear Magnetic Resonance, and Mass Spectroscopy. It explains the basic principles of spectroscopy such as how electromagnetic radiation interacts with molecules by absorption or emission of energy. The document also provides details on the instrumentation used in spectroscopy including spectrophotometers and spectrographs.
The document discusses green chemistry as a remedy for environmental pollution. It defines green chemistry as the generation of new products and processes that reduce or eliminate hazardous materials. The need for green chemistry is explained by new environmental problems, harmful side effects of some chemicals like DDT, and accidents. Advantages of green chemistry include being eco-friendly, energy efficient, producing less waste and safer products. The principles of green chemistry focus on preventing waste, improving atom economy in synthesis, using safer solvents and feedstocks, and designing for energy efficiency and degradation. Examples are given around safer chemical design and replacing hazardous solvents.
The document discusses chemistry problems and solutions presented by B.Sateesh Kumar, an assistant professor of chemistry at GDC(M)-SKLM. It includes 3 chemistry problems involving the products of reactions and Kumar's explanations of the major products formed. Specifically, it discusses hydrogenolysis to deprotect functional groups on amino acids, the reduction of an epoxide to an alcohol using LAH, and a two-step reaction sequence involving a Schmidt reaction and Boc protection.
DIBAL-H is a commercially available selective reducing agent that can reduce esters and nitriles to the corresponding aldehydes. It is prepared by heating triisobutylaluminum, which induces beta hydride elimination to form DIBAL-H and isobutene. DIBAL-H selectively reduces esters to aldehydes at low temperatures through a tetrahedral intermediate. Hydrolytic workup of this intermediate then yields the desired aldehyde products. The document provides an introduction to DIBAL-H including its preparation, applications in organic synthesis, and how it differs from other reducing agents like LiAlH4.
The document discusses sodium cyanoborohydride (NaBH3CN), including its preparation from sodium borohydride and hydrogen cyanide, properties such as being a less reactive reducing agent than sodium borohydride, solubility in solvents like THF and methanol, and ability to reduce protonated aldehydes and ketones at pH 3 but not neutral aldehydes and ketones. Main applications of sodium cyanoborohydride include its use as a reducing agent in organic synthesis reactions.
This document discusses ultraviolet-visible (UV-Vis) spectroscopy. It begins by defining spectroscopy and describing the electromagnetic radiation spectrum. It then focuses on UV-Vis spectroscopy, explaining that it involves electronic transitions in molecules caused by the absorption of ultraviolet or visible light. The major electronic transitions that can occur are defined, including σ → σ*, n → σ*, π → π*, and n → π* transitions. Factors that affect these transitions, such as conjugation, are also discussed. Real-world examples of molecular structures and the transitions they undergo are provided.
The document discusses various spectroscopic methods used in organic chemistry including UV-Visible, Infrared, Nuclear Magnetic Resonance, and Mass Spectroscopy. It explains the basic principles of spectroscopy such as how electromagnetic radiation interacts with molecules by absorption or emission of energy. The document also provides details on the instrumentation used in spectroscopy including spectrophotometers and spectrographs.
The document discusses green chemistry as a remedy for environmental pollution. It defines green chemistry as the generation of new products and processes that reduce or eliminate hazardous materials. The need for green chemistry is explained by new environmental problems, harmful side effects of some chemicals like DDT, and accidents. Advantages of green chemistry include being eco-friendly, energy efficient, producing less waste and safer products. The principles of green chemistry focus on preventing waste, improving atom economy in synthesis, using safer solvents and feedstocks, and designing for energy efficiency and degradation. Examples are given around safer chemical design and replacing hazardous solvents.
The document discusses chemistry problems and solutions presented by B.Sateesh Kumar, an assistant professor of chemistry at GDC(M)-SKLM. It includes 3 chemistry problems involving the products of reactions and Kumar's explanations of the major products formed. Specifically, it discusses hydrogenolysis to deprotect functional groups on amino acids, the reduction of an epoxide to an alcohol using LAH, and a two-step reaction sequence involving a Schmidt reaction and Boc protection.
DIBAL-H is a commercially available selective reducing agent that can reduce esters and nitriles to the corresponding aldehydes. It is prepared by heating triisobutylaluminum, which induces beta hydride elimination to form DIBAL-H and isobutene. DIBAL-H selectively reduces esters to aldehydes at low temperatures through a tetrahedral intermediate. Hydrolytic workup of this intermediate then yields the desired aldehyde products. The document provides an introduction to DIBAL-H including its preparation, applications in organic synthesis, and how it differs from other reducing agents like LiAlH4.
The document discusses sodium cyanoborohydride (NaBH3CN), including its preparation from sodium borohydride and hydrogen cyanide, properties such as being a less reactive reducing agent than sodium borohydride, solubility in solvents like THF and methanol, and ability to reduce protonated aldehydes and ketones at pH 3 but not neutral aldehydes and ketones. Main applications of sodium cyanoborohydride include its use as a reducing agent in organic synthesis reactions.
1. Chemical bonding Q & A for
PG entrance
USEFUL TO III BSc
CHEMISTRY STUDENTS
Exams-IIT JAM
CU-CET
PG-CETS
CSIR-NET
B.SATEESH KUMAR
ASSISTANT PROFESSOR IN CHEMISTRY
GDC(M)-SKLM
2. 1. In which of the following pairs, the two species are
isostructural
[కింది వాటిలో ఏది, రిండు జాతులు ఐసో స్ట్రక్చరల్ ?]
(a) SF4 and XeF4
(b) SO2
−3 and NO3
−
(c) BF3 and NF3
(d) BrO3
− and XeO3
B.SATEESH KUMAR , ASSISTANT PROFESSOR IN CHEMISTRY , GDC(M)-SKLM
All answers in Red [అన్ని సమాధానాలు ఎరుపు రంగులో ఉనాియి]
3. 2. In which one of the following molecules, the central
atom said to adopt sp2 hybridisation ?
[కింది వాటిలో ఏ కింద్ర అణువు sp2 స్టింక్చరరిక్చర్ణిం ను క్చరలిగి
ఉింది?]
(a) BeF2
(b) BF3
(c) C2H2
(d) NH3
4. 3. The correct order of electro negativity of hybrid
orbital of carbon is:
[కా్బన్ యొక్చరక స్టింక్చర్ ఆరిబటా యొక్చరక ఎలెక్్ో నెగటివిటీ యొక్చరక
స్టరైన క్చరరమిం ]
(a) sp>sp2<sp3 (b) sp>sp2>sp3
(c) sp<sp2>sp3 (d) sp<sp2<sp3
B.SATEESH KUMAR , ASSISTANT PROFESSOR IN CHEMISTRY , GDC(M)-SKLM
5. 4. In which of the following molecules/ions BF3, NO2
-
,NH2
- and H20, the central atom is sp2 hybridised?
[కింది వాటిలో ఏ అణువులు / అయానుు BF3, NO2
-, NH2
-
మరియు H20, కింద్ర అణువు sp2 స్టింక్చరరిక్చర్ణిం గల జత?]
(a) NO2
- and NH2
-
(b) NH2
- and H20
(c) NO2
- and H20
(d) BF3 and NO2
-
B.SATEESH KUMAR , ASSISTANT PROFESSOR IN CHEMISTRY ,GDC(M)-SKLM
6. 5. Which one of the following is square planar ?
[కంది వాటిలో ఏది సమతల చదరo న్నర్ాాణం ?]
(a) XeF4
(b) XeO4
(c) XeO3
(d) XeO3F2
B.SATEESH KUMAR , ASSISTANT PROFESSOR IN CHEMISTRY , GDC(M)-SKLM
7. 6. Which of the following is isoelectronic ?
[కంది వాటిలో సమ ఎలకారా న్ల జత గలది?]
(a) CO2, NO2
(b) NO−
2, CO2
(c) CN−, CO
(d) SO2, CO2
8. 7. In an octahedral structure, the pair of d orbitals
involved in d2sp3-hybridisation is
[అకా్ హెడర నిరాాణింలో, d2sp3 స్టింక్చరరిక్చర్ణిం లో ాాలగొన నన d
ఆరిబటా ల జత ఏది?]
(a) dx2−y2, dz
2
(b) dxy , dx2−y2
(c) dz
2, dxz
(d) dxy , dyz
B.SATEESH KUMAR , ASSISTANT PROFESSOR IN CHEMISTRY , GDC(M)-SKLM
9. 8. Bond order of 1.5 is shown by
[బింధ క్చరరమిం 1.5 గల అణువు ఏది?]
(a) O2
+ (b) O2
− (c) O2
2− (d) O2
B.SATEESH KUMAR , ASSISTANT PROFESSOR IN CHEMISTRY , GDC(M)-SKLM
10. 9. PCl5 is highly unstable and in solid state it exists as
into [PCl4]+ and [PCl6]- ions. The geometry of [PCl6]- is
[PCl5 చాలా అస్థి్ింగా ఉింట ింది మరియు ఘన స్థితిలో ఇది [PCl4]+
మరియు [PCl6]
- అయానుు గా ఉింట ింది. [PCl6]
- యొక్చరక జాామితి -
ఉింది]
(1) octahedral
(2) tetrahedral
(3) square pyramidal
(4) square planar
B.SATEESH KUMAR , ASSISTANT PROFESSOR IN CHEMISTRY , GDC(M)-SKLM
11. 10. Which of the following species has maximum number of
lone-pair of electrons on the central atom ?
[కింది వాటిలో ఏది కింద్ర అణువుపై గరిష్్ స్టింఖ్ాలో ఒింటరి-జత
ఎలకా్ో నును క్చరలిగి ఉింది?]
(1) XeF2
(2) H3O+
(3) XeF4
(4) XeF6
B.SATEESH KUMAR , ASSISTANT PROFESSOR IN CHEMISTRY , GDC(M)-SKLM
12. 11. In a chemical change from PCl3 → PCl5
the hybrid state of Phosphorus changes from:
[ PCl3 → PCl5 నుిండి ్సాయన మా్పులో ఫాస్టు్స్
యొక్చరక స్టింరీక్చర్ణ స్థితి మా్పు]
(1) sp2 to sp3
(2) sp3 to sp2
(3) sp3 to sp3d
(4) sp3 to dsp
B.SATEESH KUMAR , ASSISTANT PROFESSOR IN CHEMISTRY , GDC(M)-SKLM
13. 12. Which molecules/ions are most paramagnetic?
[ఏ అణువులు / అయానుు ఎక్చరుకవ
ాారాయసాకింతమైనవి?]
1. B2
2. C2
3. O2
+
4. N2
B.SATEESH KUMAR , ASSISTANT PROFESSOR IN CHEMISTRY , GDC(M)-SKLM
14. 13. The species, having bond angles of 120° is
[1200 ల బింధ క్ణo క్చరలిగి ఉనన అణువు]
(a)PH3
(b)ClF3
(c) NCl3
(d) BCl3
B.SATEESH KUMAR , ASSISTANT PROFESSOR IN CHEMISTRY , GDC(M)-SKLM
15. 14.XeF2 is isostructural with
[XeF2 తో ఐసో స్ట్రక్చరల్ (స్టమనిరాాణ) అణువు]
(a) TeF2
(b) ICI2
-
(c) SbCl3
(d) BCl3
B.SATEESH KUMAR , ASSISTANT PROFESSOR IN CHEMISTRY , GDC(M)-SKLM
16. 15. The tendency of BF3, BCl3, and BBr3 to behave as
Lewis acid decreases in the sequence
[లూయిస్ ఆము ిం వలె ప్రవరితించే BF3, BCl3 మరియు BBr3
ఆమాు ల బలిం తగన క్చరరమo]
(a) BCl3 > BF3 > BBr3
(b) BBr3 > BCI3 > BF3
(c) BBr3 > BF3 > BCl3
(d) BF3 > BCl3 > BBr3