Ruthenium and osmium are transition metals below iron in Group 8 of the Periodic Table. Fig. 4.1 shows another ruthenium complex. (i) Suggest how pyrazine is able to bond to two separate ruthenium ions. ....................................................................................................................................... . ....................................................................................................................................... . ................................................................................................................................. (ii) Pyrazine is an aromatic compound. The bonding and structure of pyrazine is similar to that of benzene. Describe and explain the shape of pyrazine. In your answer, include: - the hybridisation of the nitrogen and carbon atoms - how orbital overlap forms $$$\pi$$$ bonds between the atoms in the ring. ....................................................................................................................................... . ....................................................................................................................................... . ....................................................................................................................................... . ................................................................................................................................. (iii) Predict the number of peaks seen in the carbon-13 NMR spectrum of pyrazine. Explain your answer. ....................................................................................................................................... . ....................................................................................................................................... . ................................................................................................................................. (iv) The overall charge of the ruthenium complex in Fig. 4.1 is $$$5+$$$. Deduce the possible oxidation states of the two ruthenium ions in the complex. .................................................................................................................................

Chemistry

IGCSE&ALevel

CAIE

Exam No：9701_m24_qp_42 Year：2024 Question No：4(b)

Answer:

Knowledge points:

29.3.1 describe and explain the shape of benzene and other aromatic molecules, including sp2 hybridisation, in terms of σ bonds and a delocalised π system

29.4.1 understand that enantiomers have identical physical and chemical properties apart from their ability to rotate plane polarised light and their potential biological activity

29.4.2 understand and use the terms optically active and racemic mixture

29.4.3 describe the effect on plane polarised light of the two optical isomers of a single substance

29.4.4.1 the potential different biological activity of the two enantiomers

29.4.4.2 the need to separate a racemic mixture into two pure enantiomers

29.4.4.3 the use of chiral catalysts to produce a single pure optical isomer (Candidates should appreciate that compounds can contain more than one chiral centre, but knowledge of meso compounds and nomenclature such as diastereoisomers is not required.)

Answer:

Knowledge points:

Solution:

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